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# Basic engineering mathematics__third_edition

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### Basic engineering mathematics__third_edition

1. 1. Basic Engineering Mathematics
2. 2. In memory of Elizabeth
3. 3. Basic Engineering Mathematics Third Edition John Bird BSc(Hons), CMath, CEng, FIMA, MIEE, FIIE(Elec), FCollP Newnes OXFORD AMSTERDAM BOSTON LONDON NEW YORK PARIS SAN DIEGO SAN FRANCISCO SINGAPORE SYDNEY TOKYO
5. 5. Contents Preface xi 1. Basic arithmetic 1 1.1 Arithmetic operations 1 1.2 Highest common factors and lowest common multiples 3 1.3 Order of precedence and brackets 4 2. Fractions, decimals and percentages 6 2.1 Fractions 6 2.2 Ratio and proportion 8 2.3 Decimals 9 2.4 Percentages 11 Assignment 1 12 3. Indices and standard form 14 3.1 Indices 14 3.2 Worked problems on indices 14 3.3 Further worked problems on indices 16 3.4 Standard form 17 3.5 Worked problems on standard form 18 3.6 Further worked problems on standard form 19 4. Calculations and evaluation of formulae 20 4.1 Errors and approximations 20 4.2 Use of calculator 21 4.3 Conversion tables and charts 24 4.4 Evaluation of formulae 26 Assignment 2 28 5. Computer numbering systems 29 5.1 Binary numbers 29 5.2 Conversion of binary to denary 29 5.3 Conversion of denary to binary 30 5.4 Conversion of denary to binary via octal 31 5.5 Hexadecimal numbers 32 6. Algebra 36 6.1 Basic operations 36 6.2 Laws of Indices 38
6. 6. vi Contents 6.3 Brackets and factorization 40 6.4 Fundamental laws and precedence 42 6.5 Direct and inverse proportionality 44 Assignment 3 45 7. Simple equations 46 7.1 Expressions, equations and identities 46 7.2 Worked problems on simple equations 46 7.3 Further worked problems on simple equations 48 7.4 Practical problems involving simple equations 49 7.5 Further practical problems involving simple equations 51 8. Transposition of formulae 53 8.1 Introduction to transposition of formulae 53 8.2 Worked problems on transposition of formulae 53 8.3 Further worked problems on transposition of formulae 54 8.4 Harder worked problems on transposition of formulae 56 Assignment 4 58 9. Simultaneous equations 59 9.1 Introduction to simultaneous equations 59 9.2 Worked problems on simultaneous equations in two unknowns 59 9.3 Further worked problems on simultaneous equations 61 9.4 More difﬁcult worked problems on simultaneous equations 62 9.5 Practical problems involving simultaneous equations 64 10. Quadratic equations 68 10.1 Introduction to quadratic equations 68 10.2 Solution of quadratic equations by factorization 68 10.3 Solution of quadratic equations by ‘completing the square’ 70 10.4 Solution of quadratic equations by formula 71 10.5 Practical problems involving quadratic equations 72 10.6 The solution of linear and quadratic equations simultaneously 74 Assignment 5 75 11. Straight line graphs 76 11.1 Introduction to graphs 76 11.2 The straight line graph 76 11.3 Practical problems involving straight line graphs 81 12. Graphical solution of equations 87 12.1 Graphical solution of simultaneous equations 87 12.2 Graphical solutions of quadratic equations 88 12.3 Graphical solution of linear and quadratic equations simultaneously 92 12.4 Graphical solution of cubic equations 93 Assignment 6 94 13. Logarithms 96 13.1 Introduction to logarithms 96 13.2 Laws of logarithms 96
7. 7. Contents vii 13.3 Indicial equations 98 13.4 Graphs of logarithmic functions 99 14. Exponential functions 100 14.1 The exponential function 100 14.2 Evaluating exponential functions 100 14.3 The power series for ex 101 14.4 Graphs of exponential functions 103 14.5 Napierian logarithms 104 14.6 Evaluating Napierian logarithms 104 14.7 Laws of growth and decay 106 Assignment 7 109 15. Reduction of non-linear laws to linear form 110 15.1 Determination of law 110 15.2 Determination of law involving logarithms 112 16. Geometry and triangles 117 16.1 Angular measurement 117 16.2 Types and properties of angles 118 16.3 Properties of triangles 120 16.4 Congruent triangles 122 16.5 Similar triangles 123 16.6 Construction of triangles 125 Assignment 8 126 17. Introduction to trigonometry 128 17.1 Trigonometry 128 17.2 The theorem of Pythagoras 128 17.3 Trigonometric ratios of acute angles 129 17.4 Solution of right-angled triangles 131 17.5 Angles of elevation and depression 132 17.6 Evaluating trigonometric ratios of any angles 134 18. Trigonometric waveforms 137 18.1 Graphs of trigonometric functions 137 18.2 Angles of any magnitude 138 18.3 The production of a sine and cosine wave 140 18.4 Sine and cosine curves 141 18.5 Sinusoidal form A sin !t š a 144 Assignment 9 146 19. Cartesian and polar co-ordinates 148 19.1 Introduction 148 19.2 Changing from Cartesian into polar co-ordinates 148 19.3 Changing from polar into Cartesian co-ordinates 150 19.4 Use of R ! P and P ! R functions on calculators 151 20. Areas of plane ﬁgures 152 20.1 Mensuration 152 20.2 Properties of quadrilaterals 152
8. 8. viii Contents 20.3 Worked problems on areas of plane ﬁgures 153 20.4 Further worked problems on areas of plane ﬁgures 157 20.5 Areas of similar shapes 158 Assignment 10 159 21. The circle 160 21.1 Introduction 160 21.2 Properties of circles 160 21.3 Arc length and area of a sector 161 21.4 The equation of a circle 164 22. Volumes of common solids 166 22.1 Volumes and surface areas of regular solids 166 22.2 Worked problems on volumes and surface areas of regular solids 166 22.3 Further worked problems on volumes and surface areas of regular solids 168 22.4 Volumes and surface areas of frusta of pyramids and cones 172 22.5 Volumes of similar shapes 175 Assignment 11 175 23. Irregular areas and volumes and mean values of waveforms 177 23.1 Areas of irregular ﬁgures 177 23.2 Volumes of irregular solids 179 23.3 The mean or average value of a waveform 180 24. Triangles and some practical applications 184 24.1 Sine and cosine rules 184 24.2 Area of any triangle 184 24.3 Worked problems on the solution of triangles and their areas 184 24.4 Further worked problems on the solution of triangles and their areas 186 24.5 Practical situations involving trigonometry 187 24.6 Further practical situations involving trigonometry 190 Assignment 12 192 25. Vectors 193 25.1 Introduction 193 25.2 Vector addition 193 25.3 Resolution of vectors 195 25.4 Vector subtraction 196 25.5 Relative velocity 198 26. Number sequences 200 26.1 Simple sequences 200 26.2 The n0 th term of a series 200 26.3 Arithmetic progressions 201 26.4 Worked problems on arithmetic progression 202 26.5 Further worked problems on arithmetic progressions 203 26.6 Geometric progressions 204 26.7 Worked problems on geometric progressions 205 26.8 Further worked problems on geometric progressions 206 Assignment 13 207
9. 9. Contents ix 27. Presentation of statistical data 208 27.1 Some statistical terminology 208 27.2 Presentation of ungrouped data 209 27.3 Presentation of grouped data 212 28. Measures of central tendency and dispersion 217 28.1 Measures of central tendency 217 28.2 Mean, median and mode for discrete data 217 28.3 Mean, median and mode for grouped data 218 28.4 Standard deviation 219 28.5 Quartiles, deciles and percentiles 221 29. Probability 223 29.1 Introduction to probability 223 29.2 Laws of probability 223 29.3 Worked problems on probability 224 29.4 Further worked problems on probability 225 Assignment 14 227 30. Introduction to differentiation 229 30.1 Introduction to calculus 229 30.2 Functional notation 229 30.3 The gradient of a curve 230 30.4 Differentiation from ﬁrst principles 231 30.5 Differentiation of y D axn by the general rule 232 30.6 Differentiation of sine and cosine functions 234 30.7 Differentiation of eax and ln ax 235 30.8 Summary of standard derivatives 236 30.9 Successive differentiation 237 30.10 Rates of change 237 31. Introduction to integration 239 31.1 The process of integration 239 31.2 The general solution of integrals of the form axn 239 31.3 Standard integrals 239 31.4 Deﬁnite integrals 242 31.5 Area under a curve 243 Assignment 15 247 List of formulae 248 Answers to exercises 252 Index 267
11. 11. 1 Basic arithmetic 1.1 Arithmetic operations Whole numbers are called integers. C3, C5, C72 are called positive integers; 13, 6, 51 are called negative integers. Between positive and negative integers is the number 0 which is neither positive nor negative. The four basic arithmetic operators are: add (C), subtract ( ), multiply (ð) and divide (ł) For addition and subtraction, when unlike signs are together in a calculation, the overall sign is negative. Thus, adding minus 4 to 3 is 3C 4 and becomes 3 4 D 1. Like signs together give an overall positive sign. Thus subtract- ing minus 4 from 3 is 3 4 and becomes 3 C 4 D 7. For multiplication and division, when the numbers have unlike signs, the answer is negative, but when the numbers have like signs the answer is positive. Thus 3 ð 4 D 12, whereas 3 ð 4 D C12. Similarly 4 3 D 4 3 and 4 3 D C 4 3 Problem 1. Add 27, 74, 81 and 19 This problem is written as 27 74 C 81 19 Adding the positive integers: 27 81 Sum of positive integers is: 108 Adding the negative integers: 74 19 Sum of negative integers is: 93 Taking the sum of the negative integers from the sum of the positive integers gives: 108 93 15 Thus 27 − 74 + 81 − 19 = 15 Problem 2. Subtract 89 from 123 This is written mathematically as 123 89 123 89 34 Thus 123 − 89 = 34 Problem 3. Subtract 74 from 377 This problem is written as 377 74. Like signs together give an overall positive sign, hence 377 74 D 377 C 74 377 C74 451 Thus 377 − −74 = 451 Problem 4. Subtract 243 from 126 The problem is 126 243. When the second number is larger than the ﬁrst, take the smaller number from the larger and make the result negative.
12. 12. 2 Basic Engineering Mathematics Thus 126 243 D 243 126 243 126 117 Thus 126 − 243 = −117 Problem 5. Subtract 318 from 269 269 318. The sum of the negative integers is 269 C318 587 Thus −269 − 318 = −587 Problem 6. Multiply 74 by 13 This is written as 74 ð 13 74 13 222 74 ð 3 740 74 ð 10 Adding: 962 Thus 74 U 13 = 962 Problem 7. Multiply by 178 by 46 When the numbers have different signs, the result will be negative. (With this in mind, the problem can now be solved by multiplying 178 by 46) 178 46 1068 7120 8188 Thus 178 ð 46 D 8188 and 178 U (−46) = −8188 Problem 8. Divide l043 by 7 When dividing by the numbers 1 to 12, it is usual to use a method called short division. 1 4 9 7 103 46 3 Step 1. 7 into 10 goes 1, remainder 3. Put 1 above the 0 of 1043 and carry the 3 remainder to the next digit on the right, making it 34; Step 2. 7 into 34 goes 4, remainder 6. Put 4 above the 4 of 1043 and carry the 6 remainder to the next digit on the right, making it 63; Step 3. 7 into 63 goes 9, remainder 0. Put 9 above the 3 of 1043. Thus 1043 ÷ 7 = 149 Problem 9. Divide 378 by 14 When dividing by numbers which are larger than 12, it is usual to use a method called long division. 27 14 378 2 2 ð 14 ! 28 98 4 7 ð 14 ! 98 00 (1) 14 into 37 goes twice. Put 2 above the 7 of 378. (3) Subtract. Bring down the 8. 14 into 98 goes 7 times. Put 7 above the 8 of 378. (5) Subtract. Thus 378 ÷ 14 = 27 Problem 10. Divide 5669 by 46 This problem may be written as 5669 46 or 5669 ł 46 or 5669/46 Using the long division method shown in Problem 9 gives: 123 46 5669 46 106 92 149 138 11 As there are no more digits to bring down, 5669 ÷ 46 = 123, remainder 11 or 123 11 46 Now try the following exercise Exercise 1 Further problems on arithmetic opera- tions (Answers on page 252) In Problems 1 to 21, determine the values of the expres- sions given:
13. 13. Basic arithmetic 3 1. 67 82 C 34 2. 124 273 C 481 398 3. 927 114 C 182 183 247 4. 2417 487 C 2424 1778 4712 5. 38419 2177 C 2440 799 C 2834 6. 2715 18250 C 11471 1509 C 113274 7. 73 57 8. 813 674 9. 647 872 10. 3151 2763 11. 4872 4683 12. 23148 47724 13. 38441 53774 14. (a) 261 ð 7 (b) 462 ð 9 15. (a) 783 ð 11 (b) 73 ð 24 16. (a) 27 ð 38 (b) 77 ð 29 17. (a) 448 ð 23 (b) 143 ð 31 18. (a) 288 ł 6 (b) 979 ł 11 19. (a) 1813 7 (b) 896 16 20. (a) 21432 47 (b) 15904 ł 56 21. (a) 88738 187 (b) 46857 ł 79 1.2 Highest common factors and lowest common multiples When two or more numbers are multiplied together, the individual numbers are called factors. Thus a factor is a number which divides into another number exactly. The highest common factor (HCF) is the largest number which divides into two or more numbers exactly. A multiple is a number which contains another number an exact number of times. The smallest number which is exactly divisible by each of two or more numbers is called the lowest common multiple (LCM). Problem 11. Determine the HCF of the numbers 12, 30 and 42 Each number is expressed in terms of its lowest factors. This is achieved by repeatedly dividing by the prime numbers 2, 3, 5, 7, 11, 13 . . . (where possible) in turn. Thus 12 D 2 ð 2ð 3 30 D 2 ð 3 ð 5 42 D 2 ð 3 ð 7 The factors which are common to each of the numbers are 2 in column 1 and 3 in column 3, shown by the broken lines. Hence the HCF is 2 U 3, i.e. 6. That is, 6 is the largest number which will divide into 12, 30 and 42. Problem 12. Determine the HCF of the numbers 30, 105, 210 and 1155 Using the method shown in Problem 11: 30 D 2ð 3 ð 5 105 D 3 ð 5 ð 7 210 D 2ð 3 ð 5 ð 7 1155 D 3 ð 5 ð 7ð11 The factors which are common to each of the numbers are 3 in column 2 and 5 in column 3. Hence the HCF is 3 U 5 = 15 Problem 13. Determine the LCM of the numbers 12, 42 and 90 The LCM is obtained by ﬁnding the lowest factors of each of the numbers, as shown in Problems 11 and 12 above, and then selecting the largest group of any of the factors present. Thus 12 D 2 ð 2 ð 3 42 D 2 ð 3 ð 7 90 D 2 ð 3ð 3 ð 5 The largest group of any of the factors present are shown by the broken lines and are 2 ð2 in 12, 3 ð3 in 90, 5 in 90 and 7 in 42. Hence the LCM is 2 U 2 U 3 U 3 U 5 U 7 = 1260, and is the smallest number which 12, 42 and 90 will all divide into exactly.
14. 14. 4 Basic Engineering Mathematics Problem 14. Determine the LCM of the numbers 150, 210, 735 and 1365 Using the method shown in Problem 13 above: 150 D 2 ð 3 ð 5ð 5 210 D 2 ð 3 ð 5ð 7 735 D 3 ð 5ð 7ð 7 1365 D 3 ð 5ð 7 ð 13 The LCM is 2 U 3 U 5 U 5 U 7 U 7 U 13 = 95550 Now try the following exercise Exercise 2 Further problems on highest common factors and lowest common multiples (Answers on page 252) In Problems 1 to 6 ﬁnd (a) the HCF and (b) the LCM of the numbers given: 1. 6, 10, 14 2. 12, 30, 45 3. 10, 15, 70, 105 4. 90, 105, 300 5. 196, 210, 910, 462 6. 196, 350, 770 1.3 Order of precedence and brackets When a particular arithmetic operation is to be performed ﬁrst, the numbers and the operator(s) are placed in brackets. Thus 3 times the result of 6 minus 2 is written as 3ð 6 2 In arithmetic operations, the order in which operations are performed are: (i) to determine the values of operations contained in brackets; (ii) multiplication and division (the word ‘of’ also means multiply); and (iii) addition and subtraction. This order of precedence can be remembered by the word BODMAS, standing for Brackets, Of, Division, Multiplica- tion, Addition and Subtraction, taken in that order. The basic laws governing the use of brackets and operators are shown by the following examples: (i) 2 C 3 D 3 C 2, i.e. the order of numbers when adding does not matter; (ii) 2ð3 D 3ð2, i.e. the order of numbers when multiplying does not matter; (iii) 2 C 3 C 4 D 2 C 3 C 4, i.e. the use of brackets when adding does not affect the result; (iv) 2 ð 3 ð 4 D 2 ð 3 ð 4, i.e. the use of brackets when multiplying does not affect the result; (v) 2ð 3C4 D 2 3C4 D 2ð3C2ð4, i.e. a number placed outside of a bracket indicates that the whole contents of the bracket must be multiplied by that number; (vi) 2 C 3 4 C 5 D 5 9 D 45, i.e. adjacent brackets indicate multiplication; (vii) 2[3 C 4 ð5 ] D 2[3 C 20] D 2 ð23 D 46, i.e. when an expression contains inner and outer brackets, the inner brackets are removed ﬁrst. Problem 15. Find the value of 6 C 4 ł 5 3 The order of precedence of operations is remembered by the word BODMAS. Thus 6 C 4 ł 5 3 D 6 C 4 ł 2 (Brackets) D 6 C 2 (Division) D 8 (Addition) Problem 16. Determine the value of 13 2 ð 3 C 14 ł 2 C 5 13 2 ð 3 C 14 ł 2 C 5 D 13 2 ð 3 C 14 ł 7 (B) D 13 2 ð 3 C 2 (D) D 13 6 C 2 (M) D 15 6 (A) D 9 (S) Problem 17. Evaluate 16 ł 2 C 6 C 18[3 C 4 ð 6 21] 16ł 2 C 6 C 18[3 C 4 ð 6 21] D 16 ł 2 C 6 C 18[3 C 24 21 (B) D 16 ł 8 C 18 ð 6 (B) D 2 C 18 ð 6 (D)
15. 15. Basic arithmetic 5 D 2 C 108 (M) D 110 (A) Problem 18. Find the value of 23 4 2 ð 7 C 144 ł 4 14 8 23 4 2 ð 7 C 144 ł 4 14 8 D 23 4 ð 14 C 36 6 (B) D 23 4 ð 14 C 6 (D) D 23 56 C 6 (M) D 29 56 (A) D −27 (S) Now try the following exercise Exercise 3 Further problems on order of precedence and brackets (Answers on page 252) Simplify the expressions given in Problems 1 to 7: 1. 14 C 3 ð 15 2. 17 12 ł 4 3. 86 C 24 ł 14 2 4. 7 23 18 ł 12 5 5. 63 28 14 ł 2 C 26 6. 112 16 119 ł 17 C 3 ð 19 7. 50 14 3 C 7 16 7 7
16. 16. 2 Fractions, decimals and percentages 2.1 Fractions When 2 is divided by 3, it may be written as 2 3 or 2/3. 2 3 is called a fraction. The number above the line, i.e. 2, is called the numerator and the number below the line, i.e. 3, is called the denominator. When the value of the numerator is less than the value of the denominator, the fraction is called a proper fraction; thus 2 3 is a proper fraction. When the value of the numerator is greater than the denominator, the fraction is called an improper fraction. Thus 7 3 is an improper fraction and can also be expressed as a mixed number, that is, an integer and a proper fraction. Thus the improper fraction 7 3 is equal to the mixed number 21 3 . When a fraction is simpliﬁed by dividing the numerator and denominator by the same number, the process is called cancelling. Cancelling by 0 is not permissible. Problem 1. Simplify 1 3 C 2 7 The LCM of the two denominators is 3 ð 7, i.e. 21. Expressing each fraction so that their denominators are 21, gives: 1 3 C 2 7 D 1 3 ð 7 7 C 2 7 ð 3 3 D 7 21 C 6 21 D 7 C 6 21 D 13 21 Alternatively: Step (2) Step (3) # # 1 3 C 2 7 D 7 ð 1 C 3 ð 2 21 " Step (1) Step 1: the LCM of the two denominators; Step 2: for the fraction 1 3 , 3 into 21 goes 7 times, 7 ð the numerator is 7 ð 1; Step 3: for the fraction 2 7 , 7 into 21 goes 3 times, 3 ð the numerator is 3 ð 2. Thus 1 3 C 2 7 D 7 C 6 21 D 13 21 as obtained previously. Problem 2. Find the value of 32 3 21 6 One method is to split the mixed numbers into integers and their fractional parts. Then 3 2 3 2 1 6 D 3 C 2 3 2 C 1 6 D 3 C 2 3 2 1 6 D 1 C 4 6 1 6 D 1 3 6 D 1 1 2 Another method is to express the mixed numbers as improper fractions. Since 3 D 9 3 , then 3 2 3 D 9 3 C 2 3 D 11 3 Similarly, 2 1 6 D 12 6 C 1 6 D 13 6 Thus 3 2 3 2 1 6 D 11 3 13 6 D 22 6 13 6 D 9 6 D 1 1 2 as obtained previously. Problem 3. Evaluate 71 8 53 7
17. 17. Fractions, decimals and percentages 7 7 1 8 5 3 7 D 7 C 1 8 5 C 3 7 D 7 C 1 8 5 3 7 D 2 C 1 8 3 7 D 2 C 7 ð 1 8 ð 3 56 D 2 C 7 24 56 D 2 C 17 56 D 2 17 56 D 112 56 17 56 D 112 17 56 D 95 56 D 1 39 56 Problem 4. Determine the value of 45 8 31 4 C 12 5 4 5 8 3 1 4 C 1 2 5 D 4 3 C 1 C 5 8 1 4 C 2 5 D 2 C 5 ð 5 10 ð 1 C 8 ð 2 40 D 2 C 25 10 C 16 40 D 2 C 31 40 D 2 31 40 Problem 5. Find the value of 3 7 ð 14 15 Dividing numerator and denominator by 3 gives: 1 3 7 ð 14 15 5 D 1 7 ð 14 5 D 1 ð 14 7 ð 5 Dividing numerator and denominator by 7 gives: 1 ð 14 2 1 7 ð 5 D 1 ð 2 1 ð 5 D 2 5 This process of dividing both the numerator and denominator of a fraction by the same factor(s) is called cancelling. Problem 6. Evaluate 13 5 ð 21 3 ð 33 7 Mixed numbers must be expressed as improper fractions before multiplication can be performed. Thus, 1 3 5 ð 2 1 3 ð 3 3 7 D 5 5 C 3 5 ð 6 3 C 1 3 ð 21 7 C 3 7 D 8 5 ð 1 7 1 3 ð 24 8 7 1 D 8 ð 1 ð 8 5 ð 1 ð 1 D 64 5 D 12 4 5 Problem 7. Simplify 3 7 ł 12 21 3 7 ł 12 21 D 3 7 12 21 Multiplying both numerator and denominator by the recipro- cal of the denominator gives: 3 7 12 21 D 1 3 1 7 ð 21 3 12 4 1 12 1 21 ð 21 1 12 1 D 3 4 1 D 3 4 This method can be remembered by the rule: invert the second fraction and change the operation from division to multiplication. Thus: 3 7 ł 12 21 D 1 3 1 7 ð 21 3 12 4 D 3 4 as obtained previously. Problem 8. Find the value of 53 5 ł 71 3 The mixed numbers must be expressed as improper fractions. Thus, 5 3 5 ł 7 1 3 D 28 5 ł 22 3 D 14 28 5 ð 3 22 11 D 42 55 Problem 9. Simplify 1 3 2 5 C 1 4 ł 3 8 ð 1 3 The order of precedence of operations for problems contain- ing fractions is the same as that for integers, i.e. remem- bered by BODMAS (Brackets, Of, Division, Multiplication, Addition and Subtraction). Thus, 1 3 2 5 C 1 4 ł 3 8 ð 1 3 D 1 3 4 ð 2 C 5 ð 1 20 ł 3 1 24 8 (B) D 1 3 13 5 20 ð 8 2 1 (D) D 1 3 26 5 (M) D 5 ð 1 3 ð 26 15 (S) D 73 15 D −4 13 15
18. 18. 8 Basic Engineering Mathematics Problem 10. Determine the value of 7 6 of 3 1 2 2 1 4 C 5 1 8 ł 3 16 1 2 7 6 of 3 1 2 2 1 4 C 5 1 8 ł 3 16 1 2 D 7 6 of 1 1 4 C 41 8 ł 3 16 1 2 (B) D 7 6 ð 5 4 C 41 8 ł 3 16 1 2 (O) D 7 6 ð 5 4 C 41 1 8 ð 16 2 3 1 2 (D) D 35 24 C 82 3 1 2 (M) D 35 C 656 24 1 2 (A) D 691 24 1 2 (A) D 691 12 24 (S) D 679 24 D 28 7 24 Now try the following exercise Exercise 4 Further problems on fractions (Answers on page 252) Evaluate the expressions given in Problems 1 to 13: 1. (a) 1 2 C 2 5 (b) 7 16 1 4 2. (a) 2 7 C 3 11 (b) 2 9 1 7 C 2 3 3. (a) 5 3 13 C 3 3 4 (b) 4 5 8 3 2 5 4. (a) 10 3 7 8 2 3 (b) 3 1 4 4 4 5 C 1 5 6 5. (a) 3 4 ð 5 9 (b) 17 35 ð 15 119 6. (a) 3 5 ð 7 9 ð 1 2 7 (b) 13 17 ð 4 7 11 ð 3 4 39 7. (a) 1 4 ð 3 11 ð 1 5 39 (b) 3 4 ł 1 4 5 8. (a) 3 8 ł 45 64 (b) 1 1 3 ł 2 5 9 9. 1 3 3 4 ð 16 27 10. 1 2 C 3 5 ł 9 15 1 3 11. 7 15 of 15 ð 5 7 C 3 4 ł 15 16 12. 1 4 ð 2 3 1 3 ł 3 5 C 2 7 13. 2 3 ð 1 1 4 ł 2 3 C 1 4 C 1 3 5 2.2 Ratio and proportion The ratio of one quantity to another is a fraction, and is the number of times one quantity is contained in another quantity of the same kind. If one quantity is directly proportional to another, then as one quantity doubles, the other quantity also doubles. When a quantity is inversely proportional to another, then as one quantity doubles, the other quantity is halved. Problem 11. Divide 126 in the ratio of 5 to 13 Because the ratio is to be 5 parts to 13 parts, then the total number of parts is 5 C 13, that is 18. Then, 18 parts correspond to 126 Hence 1 part corresponds to 126 18 D 7, 5 parts correspond to 5 ð 7 D 35 and 13 parts correspond to 13 ð 7 D 91 (Check: the parts must add up to the total 35 C 91 D 126 D the total.) Problem 12. A piece of timber 273 cm long is cut into three pieces in the ratio of 3 to 7 to 11. Determine the lengths of the three pieces. The total number of parts is 3 C 7 C 11, that is, 21. Hence 21 parts correspond to 273 cm 1 part corresponds to 273 21 D 13 cm 3 parts correspond to 3 ð 13 D 39 cm 7 parts correspond to 7 ð 13 D 91 cm 11 parts correspond to 11 ð 13 D 143 cm i.e. the lengths of the three pieces are 39 cm, 91 cm and 143 cm. (Check: 39 C 91 C 143 D 273)
20. 20. 10 Basic Engineering Mathematics The numbers are written so that the decimal points are under each other. Each column is added, starting from the right. 42.7 3.04 8.7 0.06 54.50 Thus 42.7 + 3.04 + 8.7 + 0.06 = 54.50 Problem 18. Take 81.70 from 87.23 The numbers are written with the decimal points under each other. 87.23 81.70 5.53 Thus 87.23 − 81.70 = 5.53 Problem 19. Find the value of 23.4 17.83 57.6 C 32.68 The sum of the positive decimal fractions is 23.4 C 32.68 D 56.08 The sum of the negative decimal fractions is 17.83 C 57.6 D 75.43 Taking the sum of the negative decimal fractions from the sum of the positive decimal fractions gives: 56.08 75.43 i.e. 75.43 56.08 D −19.35 Problem 20. Determine the value of 74.3 ð 3.8 When multiplying decimal fractions: (i) the numbers are multiplied as if they are integers, and (ii) the position of the decimal point in the answer is such that there are as many digits to the right of it as the sum of the digits to the right of the decimal points of the two numbers being multiplied together. Thus (i) 743 38 5944 22 290 28 234 (ii) As there are 1C1 D 2 digits to the right of the decimal points of the two numbers being multiplied together, (74.3 ð 3.8), then 74.3 U 3.8 = 282.34 Problem 21. Evaluate 37.81 ł 1.7, correct to (i) 4 signiﬁcant ﬁgures and (ii) 4 decimal places. 37.81 ł 1.7 D 37.81 1.7 The denominator is changed into an integer by multiplying by 10. The numerator is also multiplied by 10 to keep the fraction the same. Thus 37.81 ł 1.7 D 37.81 ð 10 1.7 ð 10 D 378.1 17 The long division is similar to the long division of integers and the ﬁrst four steps are as shown: 22.24117.. 17 378.100000 34 38 34 41 34 70 68 20 (i) 37.81 ÷ 1.7 = 22.24, correct to 4 signiﬁcant ﬁgures, and (ii) 37.81 ÷ 1.7 = 22.2412, correct to 4 decimal places. Problem 22. Convert (a) 0.4375 to a proper fraction and (b) 4.285 to a mixed number. (a) 0.4375 can be written as 0.4375 ð 10 000 10 000 without chang- ing its value, i.e. 0.4375 D 4375 10 000 By cancelling 4375 10 000 D 875 2000 D 175 400 D 35 80 D 7 16 i.e. 0.4375 = 7 16 (b) Similarly, 4.285 D 4 285 1000 D 4 57 200
21. 21. Fractions, decimals and percentages 11 Problem 23. Express as decimal fractions: (a) 9 16 and (b) 5 7 8 (a) To convert a proper fraction to a decimal fraction, the numerator is divided by the denominator. Division by 16 can be done by the long division method, or, more simply, by dividing by 2 and then 8: 4.50 2 9.00 0.5 6 2 5 8 4.55 02 04 0 Thus, 9 16 = 0.5625 (b) For mixed numbers, it is only necessary to convert the proper fraction part of the mixed number to a decimal fraction. Thus, dealing with the 7 8 gives: 0.875 8 7.000 i.e. 7 8 D 0.875 Thus 5 7 8 = 5.875 Now try the following exercise Exercise 6 Further problems on decimals (Answers on page 252) In Problems 1 to 7, determine the values of the expres- sions given: 1. 23.6 C 14.71 18.9 7.421 2. 73.84 113.247 C 8.21 0.068 3. 5.73 ð 4.2 4. 3.8 ð 4.1 ð 0.7 5. 374.1 ð 0.006 6. 421.8 ł 17, (a) correct to 4 signiﬁcant ﬁgures and (b) correct to 3 decimal places. 7. 0.0147 2.3 , (a) correct to 5 decimal places and (b) correct to 2 signiﬁcant ﬁgures. 8. Convert to proper fractions: (a) 0.65 (b) 0.84 (c) 0.0125 (d) 0.282 and (e) 0.024 9. Convert to mixed numbers: (a) 1.82 (b) 4.275 (c) 14.125 (d) 15.35 and (e) 16.2125 In Problems 10 to 15, express as decimal fractions to the accuracy stated: 10. 4 9 , correct to 5 signiﬁcant ﬁgures. 11. 17 27 , correct to 5 decimal place. 12. 1 9 16 , correct to 4 signiﬁcant ﬁgures. 13. 53 5 11 , correct to 3 decimal places. 14. 13 31 37 , correct to 2 decimal places. 15. 8 9 13 , correct to 3 signiﬁcant ﬁgures. 2.4 Percentages Percentages are used to give a common standard and are fractions having the number 100 as their denominators. For example, 25 per cent means 25 100 i.e. 1 4 and is written 25%. Problem 24. Express as percentages: (a) 1.875 and (b) 0.0125 A decimal fraction is converted to a percentage by multiply- ing by 100. Thus, (a) 1.875 corresponds to 1.875 ð 100%, i.e. 187.5% (b) 0.0125 corresponds to 0.0125 ð 100%, i.e. 1.25% Problem 25. Express as percentages: (a) 5 16 and (b) 1 2 5 To convert fractions to percentages, they are (i) converted to decimal fractions and (ii) multiplied by 100 (a) By division, 5 16 D 0.3125, hence 5 16 corresponds to 0.3125 ð 100%, i.e. 31.25% (b) Similarly, 1 2 5 D 1.4 when expressed as a decimal fraction. Hence 1 2 5 D 1.4 ð 100% D 140% Problem 26. It takes 50 minutes to machine a certain part. Using a new type of tool, the time can be reduced by 15%. Calculate the new time taken. 15% of 50 minutes D 15 100 ð 50 D 750 100 D 7.5 minutes.
22. 22. 12 Basic Engineering Mathematics Hence the new time taken is 50 7.5 D 42.5 minutes. Alternatively, if the time is reduced by 15%, then it now takes 85% of the original time, i.e. 85% of 50 D 85 100 ð50 D 4250 100 D 42.5 minutes, as above. Problem 27. Find 12.5% of £378 12.5% of £378 means 12.5 100 ð378, since per cent means ‘per hundred’. Hence 12.5% of £378 D 12.5 1 100 8 ð 378 D 378 8 D £47.25 Problem 28. Express 25 minutes as a percentage of 2 hours, correct to the nearest 1%. Working in minute units, 2 hours D 120 minutes. Hence 25 minutes is 25 120 ths of 2 hours. By cancelling, 25 120 D 5 24 Expressing 5 24 as a decimal fraction gives 0.208P3 Multiplying by 100 to convert the decimal fraction to a percentage gives: 0.208P3 ð 100 D 20.8P3% Thus 25 minutes is 21% of 2 hours, correct to the near- est 1%. Problem 29. A German silver alloy consists of 60% copper, 25% zinc and 15% nickel. Determine the masses of the copper, zinc and nickel in a 3.74 kilogram block of the alloy. By direct proportion: 100% corresponds to 3.74 kg 1% corresponds to 3.74 100 D 0.0374 kg 60% corresponds to 60 ð 0.0374 D 2.244 kg 25% corresponds to 25 ð 0.0374 D 0.935 kg 15% corresponds to 15 ð 0.0374 D 0.561 kg Thus, the masses of the copper, zinc and nickel are 2.244 kg, 0.935 kg and 0.561 kg, respectively. (Check: 2.244 C 0.935 C 0.561 D 3.74) Now try the following exercise Exercise 7 Further problems percentages (Answers on page 253) 1. Convert to percentages: (a) 0.057 (b) 0.374 (c) 1.285 2. Express as percentages, correct to 3 signiﬁcant ﬁgures: (a) 7 33 (b) 19 24 (c) 1 11 16 3. Calculate correct to 4 signiﬁcant ﬁgures: (a) 18% of 2758 tonnes (b) 47% of 18.42 grams (c) 147% of 14.1 seconds 4. When 1600 bolts are manufactured, 36 are unsatisfac- tory. Determine the percentage unsatisfactory. 5. Express: (a) 140 kg as a percentage of 1 t (b) 47 s as a percentage of 5 min (c) 13.4 cm as a percentage of 2.5 m 6. A block of monel alloy consists of 70% nickel and 30% copper. If it contains 88.2 g of nickel, determine the mass of copper in the block. 7. A drilling machine should be set to 250 rev/min. The nearest speed available on the machine is 268 rev/min. Calculate the percentage overspeed. 8. Two kilograms of a compound contains 30% of ele- ment A, 45% of element B and 25% of element C. Determine the masses of the three elements present. 9. A concrete mixture contains seven parts by volume of ballast, four parts by volume of sand and two parts by volume of cement. Determine the percentage of each of these three constituents correct to the nearest 1% and the mass of cement in a two tonne dry mix, correct to 1 signiﬁcant ﬁgure. Assignment 1 This assignment covers the material contained in Chapters 1 and 2. The marks for each question are shown in brackets at the end of each question. 1. Evaluate the following: (a) 2016 593 (b) 73 C 35 ł 11 4
23. 23. Fractions, decimals and percentages 13 (c) 120 15 133 ł 19 C 2 ð 17 (d) 2 5 1 15 C 5 6 (e) 49.31 97.763 C 9.44 0.079 (14) 2. Determine, by long multiplication 37 ð 42 (3) 3. Evaluate, by long division 4675 11 (3) 4. Find (a) the highest common factor, and (b) the low- est common multiple of the following numbers: 15 40 75 120 (6) 5. Simplify (a) 2 2 3 ł 3 1 3 (b) 1 4 7 ð 2 1 4 ł 1 3 C 1 5 C 2 7 24 (9) 6. A piece of steel, 1.69 m long, is cut into three pieces in the ratio 2 to 5 to 6. Determine, in centimeters, the lengths of the three pieces. (4) 7. Evaluate 576.29 19.3 (a) correct to 4 signiﬁcant ﬁgures (b) correct to 1 decimal place (4) 8. Express 7 9 46 correct to 2 decimal places (2) 9. Determine, correct to 1 decimal places, 57% of 17.64 g (2) 10. Express 54.7 mm as a percentage of 1.15 m, correct to 3 signiﬁcant ﬁgures. (3)
24. 24. 3 Indices and standard form 3.1 Indices The lowest factors of 2000 are 2 ð 2 ð 2 ð 2 ð 5 ð 5 ð 5. These factors are written as 24 ð53 , where 2 and 5 are called bases and the numbers 4 and 3 are called indices. When an index is an integer it is called a power. Thus, 24 is called ‘two to the power of four’, and has a base of 2 and an index of 4. Similarly, 53 is called ‘ﬁve to the power of 3’ and has a base of 5 and an index of 3. Special names may be used when the indices are 2 and 3, these being called ‘squared’ and ‘cubed’, respectively. Thus 72 is called ‘seven squared’ and 93 is called ‘nine cubed’. When no index is shown, the power is 1, i.e. 2 means 21 . Reciprocal The reciprocal of a number is when the index is 1 and its value is given by 1 divided by the base. Thus the reciprocal of 2 is 2 1 and its value is 1 2 or 0.5. Similarly, the reciprocal of 5 is 5 1 which means 1 5 or 0.2 Square root The square root of a number is when the index is 1 2 , and the square root of 2 is written as 21/2 or p 2. The value of a square root is the value of the base which when multiplied by itself gives the number. Since 3 ð 3 D 9, then p 9 D 3. However, 3 ð 3 D 9, so p 9 D 3. There are always two answers when ﬁnding the square root of a number and this is shown by putting both a C and a sign in front of the answer to a square root problem. Thus p 9 D š3 and 41/2 D p 4 D š2, and so on. Laws of indices When simplifying calculations involving indices, certain basic rules or laws can be applied, called the laws of indices. These are given below. (i) When multiplying two or more numbers having the same base, the indices are added. Thus 32 ð 34 D 32C4 D 36 (ii) When a number is divided by a number having the same base, the indices are subtracted. Thus 35 32 D 35 2 D 33 (iii) When a number which is raised to a power is raised to a further power, the indices are multiplied. Thus 35 2 D 35ð2 D 310 (iv) When a number has an index of 0, its value is 1. Thus 30 D 1 (v) A number raised to a negative power is the reciprocal of that number raised to a positive power. Thus 3 4 D 1 34 Similarly, 1 2 3 D 23 (vi) When a number is raised to a fractional power the denominator of the fraction is the root of the number and the numerator is the power. Thus 82/3 D 3 p 82 D 2 2 D 4 and 251/2 D 2 p 251 D p 251 D š5 (Note that p Á 2 p ) 3.2 Worked problems on indices Problem 1. Evaluate: (a) 52 ð 53 , (b) 32 ð 34 ð 3 and (c) 2 ð 22 ð 25
25. 25. Indices and standard form 15 From law (i): (a) 52 ð 53 D 5 2C3 D 55 D 5 ð 5 ð 5 ð 5 ð 5 D 3125 (b) 32 ð 34 ð 3 D 3 2C4C1 D 37 D 3 ð 3 ð . . . to 7 terms D 2187 (c) 2 ð 22 ð 25 D 2 1C2C5 D 28 D 256 Problem 2. Find the value of: (a) 75 73 and (b) 57 54 From law (ii): (a) 75 73 D 7 5 3 D 72 D 49 (b) 57 54 D 5 7 4 D 53 D 125 Problem 3. Evaluate: (a) 52 ð 53 ł 54 and (b) 3 ð 35 ł 32 ð 33 From laws (i) and (ii): (a) 52 ð 53 ł 54 D 52 ð 53 54 D 5 2C3 54 D 55 54 D 5 5 4 D 51 D 5 (b) 3 ð 35 ł 32 ð 33 D 3 ð 35 32 ð 33 D 3 1C5 3 2C3 D 36 35 D 36 5 D 31 D 3 Problem 4. Simplify: (a) 23 4 (b) 32 5 , expressing the answers in index form. From law (iii): (a) 23 4 D 23ð4 D 212 (b) 32 5 D 32ð5 D 310 Problem 5. Evaluate: 102 3 104 ð 102 From the laws of indices: 102 3 104 ð 102 D 10 2ð3 10 4C2 D 106 106 D 106 6 D 100 D 1 Problem 6. Find the value of (a) 23 ð 24 27 ð 25 and (b) 32 3 3 ð 39 From the laws of indices: (a) 23 ð 24 27 ð 25 D 2 3C4 2 7C5 D 27 212 D 27 12 D 2 5 D 1 25 D 1 32 (b) 32 3 3 ð 39 D 32ð3 31C9 D 36 310 D 36 10 D 3 4 D 1 34 D 1 81 Problem 7. Evaluate (a) 41/2 (b) 163/4 (c) 272/3 (d) 9 1/2 (a) 41/2 D p 4 D ±2 (b) 163/4 D 4 p 163 D 2 3 D 8 (Note that it does not matter whether the 4th root of 16 is found ﬁrst or whether 16 cubed is found ﬁrst–the same answer will result.) (c) 272/3 D 3 p 272 D 3 2 D 9 (d) 9 1/2 D 1 91/2 D 1 p 9 D 1 š3 D ± 1 3 Now try the following exercise Exercise 8 Further problems on indices (Answers on page 253) In Problems 1 to 12, simplify the expressions given, expressing the answers in index form and with positive indices: 1. (a) 33 ð 34 (b) 42 ð 43 ð 44 2. (a) 23 ð 2 ð 22 (b) 72 ð 74 ð 7 ð 73 3. (a) 24 23 (b) 37 32 4. (a) 56 ł 53 (b) 713 /710 5. (a) 72 3 (b) 33 2 6. (a) 153 5 (b) 172 4 7. (a) 22 ð 23 24 (b) 37 ð 34 35 8. (a) 57 52 ð 53 (b) 135 13 ð 132
26. 26. 16 Basic Engineering Mathematics 9. (a) 9 ð 32 3 3 ð 27 2 (b) 16 ð 4 2 2 ð 8 3 10. (a) 5 2 5 4 (b) 32 ð 3 4 33 11. (a) 72 ð 7 3 7 ð 7 4 (b) 23 ð 2 4 ð 25 2 ð 2 2 ð 26 12. (a) 13 ð 13 2 ð 134 ð 13 3 (b) 5 7 ð 52 5 8 ð 53 3.3 Further worked problems on indices Problem 8. Evaluate 33 ð 57 53 ð 34 The laws of indices only apply to terms having the same base. Grouping terms having the same base, and then apply- ing the laws of indices to each of the groups independently gives: 33 ð 57 53 ð 34 D 33 34 ð 57 53 D 3 3 4 ð 5 7 3 D 3 1 ð 54 D 54 31 D 625 3 D 208 1 3 Problem 9. Find the value of 23 ð 35 ð 72 2 74 ð 24 ð 33 23 ð 35 ð 72 2 74 ð 24 ð 33 D 23 4 ð 35 3 ð 72ð2 4 D 2 1 ð 32 ð 70 D 1 2 ð 32 ð 1 D 9 2 D 4 1 2 Problem 10. Evaluate: 41.5 ð 81/3 22 ð 32 2/5 41.5 D 43/2 D p 43 D 23 D 8, 81/3 D 3 p 8 D 2, 22 D 4 32 2/5 D 1 322/5 D 1 5 p 322 D 1 22 D 1 4 Hence 41.5 ð 81/3 22 ð 32 2/5 D 8 ð 2 4 ð 1 4 D 16 1 D 16 Alternatively, 41.5 ð 81/3 22 ð 32 2/5 D [ 2 2 ]3/2 ð 23 1/3 22 ð 25 2/5 D 23 ð 21 22 ð 2 2 D 23C1 2 2 D 24 D 16 Problem 11. Evaluate: 32 ð 55 C 33 ð 53 34 ð 54 Dividing each term by the HCF (i.e. highest common factor) of the three terms, i.e. 32 ð 53 , gives: 32 ð 55 C 33 ð 53 34 ð 54 D 32 ð 55 32 ð 53 C 33 ð 53 32 ð 53 34 ð 54 32 ð 53 D 3 2 2 ð 5 5 3 C 3 3 2 ð 50 3 4 2 ð 5 4 3 D 30 ð 52 C 31 ð 50 32 ð 51 D 1 ð 25 C 3 ð 1 9 ð 5 D 28 45 Problem 12. Find the value of 32 ð 55 34 ð 54 C 33 ð 53 To simplify the arithmetic, each term is divided by the HCF of all the terms, i.e. 32 ð 53 . Thus 32 ð 55 34 ð 54 C 33 ð 53 D 32 ð 55 32 ð 53 34 ð 54 32 ð 53 C 33 ð 53 32 ð 53 D 3 2 2 ð 5 5 3 3 4 2 ð 5 4 3 C 3 3 2 ð 5 3 3 D 30 ð 52 32 ð 51 C 31 ð 50 D 25 45 C 3 D 25 48 Problem 13. Simplify 7 3 ð 34 3 2 ð 75 ð 5 2 , expressing the answer in index form with positive indices. Since 7 3 D 1 73 , 1 3 2 D 32 and 1 5 2 D 52 then 7 3 ð 34 3 2 ð 75 ð 5 2 D 34 ð 32 ð 52 73 ð 75 D 3 4C2 ð 52 7 3C5 D 36 U 52 78
27. 27. Indices and standard form 17 Problem 14. Simplify 162 ð 9 2 4 ð 33 2 3 ð 82 expressing the answer in index form with positive indices. Expressing the numbers in terms of their lowest prime numbers gives: 162 ð 9 2 4 ð 33 2 3 ð 82 D 24 2 ð 32 2 22 ð 33 2 3 ð 23 2 D 28 ð 3 4 22 ð 33 2 3 ð 26 D 28 ð 3 4 22 ð 33 23 Dividing each term by the HCF (i.e. 22 ) gives: 28 ð 3 4 22 ð 33 23 D 26 ð 3 4 33 2 D 26 34(33 − 2) Problem 15. Simplify 4 3 3 ð 3 5 2 2 5 3 giving the answer with positive indices. A fraction raised to a power means that both the numerator and the denominator of the fraction are raised to that power, i.e. 4 3 3 D 43 33 A fraction raised to a negative power has the same value as the inverse of the fraction raised to a positive power. Thus, 3 5 2 D 1 3 5 2 D 1 32 52 D 1 ð 52 32 D 52 32 Similarly, 2 5 3 D 5 2 3 D 53 23 Thus, 4 3 3 ð 3 5 2 2 5 3 D 43 33 ð 52 32 53 23 D 43 33 ð 52 32 ð 23 53 D 22 3 ð 23 3 3C2 ð 5 3 2 D 29 35 U 5 Now try the following exercise Exercise 9 Further problems on indices (Answers on page 253) In Problems 1 and 2, simplify the expressions given, expressing the answers in index form and with positive indices: 1. (a) 33 ð 52 54 ð 34 (b) 7 2 ð 3 2 35 ð 74 ð 7 3 2. (a) 42 ð 93 83 ð 34 (b) 8 2 ð 52 ð 3 4 252 ð 24 ð 9 2 3. Evaluate (a) 1 32 1 (b) 810.25 (c) 16 1/4 (d) 4 9 1/2 In problems 4 to 10, evaluate the expressions given. 4. 92 ð 74 34 ð 74 C 33 ð 72 5. 33 ð 52 23 ð 32 82 ð 9 6. 33 ð 72 52 ð 73 32 ð 5 ð 72 7. 24 2 3 2 ð 44 23 ð 162 8. 1 2 3 2 3 2 3 5 2 9. 4 3 4 2 9 2 10. 32 3/2 ð 81/3 2 3 2 ð 43 1/2 ð 9 1/2 3.4 Standard form A number written with one digit to the left of the decimal point and multiplied by 10 raised to some power is said to be written in standard form. Thus: 5837 is written as 5.837 ð 103 in standard form, and 0.0415 is written as 4.15 ð 10 2 in standard form. When a number is written in standard form, the ﬁrst factor is called the mantissa and the second factor is called the exponent. Thus the number 5.8 ð 103 has a mantissa of 5.8 and an exponent of 103 (i) Numbers having the same exponent can be added or subtracted in standard form by adding or subtracting the mantissae and keeping the exponent the same. Thus: 2.3 ð 104 C 3.7 ð 104 D 2.3 C 3.7 ð 104 D 6.0 ð 104 and 5.9 ð 10 2 4.6 ð 10 2 D 5.9 4.6 ð 10 2 D 1.3 ð 10 2
28. 28. 18 Basic Engineering Mathematics When the numbers have different exponents, one way of adding or subtracting the numbers is to express one of the numbers in non-standard form, so that both numbers have the same exponent. Thus: 2.3 ð 104 C 3.7 ð 103 D 2.3 ð 104 C 0.37 ð 104 D 2.3 C 0.37 ð 104 D 2.67 ð 104 Alternatively, 2.3 ð 104 C 3.7 ð 103 D 23 000 C 3700 D 26 700 D 2.67 ð 104 (ii) The laws of indices are used when multiplying or divid- ing numbers given in standard form. For example, 2.5 ð 103 ð 5 ð 102 D 2.5 ð 5 ð 103C2 D 12.5 ð 105 or 1.25 ð 106 Similarly, 6 ð 104 1.5 ð 102 D 6 1.5 ð 104 2 D 4 ð 102 3.5 Worked problems on standard form Problem 16. Express in standard form: (a) 38.71 (b) 3746 (c) 0.0124 For a number to be in standard form, it is expressed with only one digit to the left of the decimal point. Thus: (a) 38.71 must be divided by 10 to achieve one digit to the left of the decimal point and it must also be multiplied by 10 to maintain the equality, i.e. 38.71 D 38.71 10 ð 10 D 3.871 U 10 in standard form (b) 3746 D 3746 1000 ð 1000 D 3.746 U 103 in standard form. (c) 0.0124 D 0.0124 ð 100 100 D 1.24 100 D 1.24 U 10−2 in standard form Problem 17. Express the following numbers, which are in standard form, as decimal numbers: (a) 1.725 ð 10 2 (b) 5.491 ð 104 (c) 9.84 ð 100 (a) 1.725 ð 10 2 D 1.725 100 D 0.01725 (b) 5.491 ð 104 D 5.491 ð 10 000 D 54 910 (c) 9.84 ð 100 D 9.84 ð 1 D 9.84 (since 100 D 1) Problem 18. Express in standard form, correct to 3 signiﬁcant ﬁgures: (a) 3 8 (b) 19 2 3 (c) 741 9 16 (a) 3 8 D 0.375, and expressing it in standard form gives: 0.375 D 3.75 U 10−1 (b) 19 2 3 D 19.P6 D 1.97 U 10 in standard form, correct to 3 signiﬁcant ﬁgures. (c) 741 9 16 D 741.5625 D 7.42 U 102 in standard form, correct to 3 signiﬁcant ﬁgures. Problem 19. Express the following numbers, given in standard form, as fractions or mixed numbers: (a) 2.5 ð 10 1 (b) 6.25 ð 10 2 (c) 1.354 ð 102 (a) 2.5 ð 10 1 D 2.5 10 D 25 100 D 1 4 (b) 6.25 ð 10 2 D 6.25 100 D 625 10 000 D 1 16 (c) 1.354 ð 102 D 135.4 D 135 4 10 D 135 2 5 Now try the following exercise Exercise 10 Further problems on standard form (Answers on page 253) In Problems 1 to 5, express in standard form: 1. (a) 73.9 (b) 28.4 (c) 197.72 2. (a) 2748 (b) 33170 (c) 274218 3. (a) 0.2401 (b) 0.0174 (c) 0.00923 4. (a) 1702.3 (b) 10.04 (c) 0.0109 5. (a) 1 2 (b) 11 7 8 (c) 130 3 5 (d) 1 32 In Problems 6 and 7, express the numbers given as integers or decimal fractions: 6. (a) 1.01 ð 103 (b) 9.327 ð 102 (c) 5.41 ð 104 (d) 7 ð 100 7. (a) 3.89 ð 10 2 (b) 6.741 ð 10 1 (c) 8 ð 10 3
29. 29. Indices and standard form 19 3.6 Further worked problems on standard form Problem 20. Find the value of (a) 7.9 ð 10 2 5.4 ð 10 2 (b) 8.3 ð 103 C 5.415 ð 103 and (c) 9.293 ð 102 C 1.3 ð 103 expressing the answers in standard form. Numbers having the same exponent can be added or sub- tracted by adding or subtracting the mantissae and keeping the exponent the same. Thus: (a) 7.9 ð 10 2 5.4 ð 10 2 D 7.9 5.4 ð 10 2 D 2.5 U 10−2 (b) 8.3 ð 103 C 5.415 ð 103 D 8.3 C 5.415 ð 103 D 13.715 ð 103 D 1.3715 U 104 in standard form. (c) Since only numbers having the same exponents can be added by straight addition of the mantissae, the numbers are converted to this form before adding. Thus: 9.293 ð 102 C 1.3 ð 103 D 9.293 ð 102 C 13 ð 102 D 9.293 C 13 ð 102 D 22.293 ð 102 D 2.2293 U 103 in standard form. Alternatively, the numbers can be expressed as decimal fractions, giving: 9.293 ð 102 C 1.3 ð 103 D 929.3 C 1300 D 2229.3 D 2.2293 U 103 in standard form as obtained previously. This method is often the ‘safest’ way of doing this type of problem. Problem 21. Evaluate (a) 3.75 ð 103 6 ð 104 and (b) 3.5 ð 105 7 ð 102 expressing answers in standard form. (a) 3.75 ð 103 6 ð 104 D 3.75 ð 6 103C4 D 22.50 ð 107 D 2.25 U 108 (b) 3.5 ð 105 7 ð 102 D 3.5 7 ð 105 2 D 0.5 ð 103 D 5 U 102 Now try the following exercise Exercise 11 Further problems on standard form (Answers on page 253) In Problems 1 to 4, ﬁnd values of the expressions given, stating the answers in standard form: 1. (a) 3.7 ð 102 C 9.81 ð 102 (b) 1.431 ð 10 1 C 7.3 ð 10 1 (c) 8.414 ð 10 2 2.68 ð 10 2 2. (a) 4.831 ð 102 C 1.24 ð 103 (b) 3.24 ð 10 3 1.11 ð 10 4 (c) 1.81 ð 102 C 3.417 ð 102 C 5.972 ð 102 3. (a) 4.5 ð 10 2 3 ð 103 (b) 2 ð 5.5 ð 104 4. (a) 6 ð 10 3 3 ð 10 5 (b) 2.4 ð 103 3 ð 10 2 4.8 ð 104 5. Write the following statements in standard form. (a) The density of aluminium is 2710 kg m 3 (b) Poisson’s ratio for gold is 0.44 (c) The impedance of free space is 376.73 (d) The electron rest energy is 0.511 MeV (e) Proton charge-mass ratio is 95 789 700 C kg 1 (f) The normal volume of a perfect gas is 0.02241 m3 mol 1
30. 30. 4 Calculations and evaluation of formulae 4.1 Errors and approximations (i) In all problems in which the measurement of distance, time, mass or other quantities occurs, an exact answer cannot be given; only an answer which is correct to a stated degree of accuracy can be given. To take account of this an error due to measurement is said to exist. (ii) To take account of measurement errors it is usual to limit answers so that the result given is not more than one signiﬁcant ﬁgure greater than the least accurate number given in the data. (iii) Rounding-off errors can exist with decimal fractions. For example, to state that p D 3.142 is not strictly correct, but ‘p D 3.142 correct to 4 signiﬁcant ﬁgures’ is a true statement. (Actually, p D 3.14159265 . . .) (iv) It is possible, through an incorrect procedure, to obtain the wrong answer to a calculation. This type of error is known as a blunder. (v) An order of magnitude error is said to exist if incorrect positioning of the decimal point occurs after a calcula- tion has been completed. (vi) Blunders and order of magnitude errors can be reduced by determining approximate values of calculations. Answers which do not seem feasible must be checked and the calculation must be repeated as necessary. An engineer will often need to make a quick mental approximation for a calculation. For example, 49.1 ð 18.4 ð 122.1 61.2 ð 38.1 may be approximated to 50 ð 20 ð 120 60 ð 40 and then, by cancelling, 50 ð 1 20 ð 120 2 1 1 60 ð 40 2 1 D 50. An accurate answer somewhere between 45 and 55 could therefore be expected. Certainly an answer around 500 or 5 would not be expected. Actually, by calculator 49.1 ð 18.4 ð 122.1 61.2 ð 38.1 D 47.31, correct to 4 signiﬁcant ﬁgures. Problem 1. The area A of a triangle is given by A D 1 2 bh. The base b when measured is found to be 3.26 cm, and the perpendicular height h is 7.5 cm. Deter- mine the area of the triangle. Area of triangle D 1 2 bh D 1 2 ð 3.26 ð 7.5 D 12.225 cm2 (by calculator). The approximate value is 1 2 ð3ð8 D 12 cm2 , so there are no obvious blunder or magnitude errors. However, it is not usual in a measurement type problem to state the answer to an accuracy greater than 1 signiﬁcant ﬁgure more than the least accurate number in the data: this is 7.5 cm, so the result should not have more than 3 signiﬁcant ﬁgures Thus area of triangle = 12.2 cm2 Problem 2. State which type of error has been made in the following statements: (a) 72 ð 31.429 D 2262.9 (b) 16 ð 0.08 ð 7 D 89.6 (c) 11.714 ð 0.0088 D 0.3247, correct to 4 decimal places. (d) 29.74 ð 0.0512 11.89 D 0.12, correct to 2 signiﬁcant ﬁgures.
32. 32. 22 Basic Engineering Mathematics Problem 5. Evaluate the following, correct to 4 deci- mal places: (a) 46.32 ð 97.17 ð 0.01258 (b) 4.621 23.76 (c) 1 2 62.49 ð 0.0172 (a) 46.32 ð 97.17 ð 0.01258 D 56.6215031 . . . D 56.6215, correct to 4 decimal places. (b) 4.621 23.76 D 0.19448653 . . . D 0.1945, correct to 4 decimal places. (c) 1 2 62.49 ð 0.0172 D 0.537414 D 0.5374, correct to 4 decimal places. Problem 6. Evaluate the following, correct to 3 deci- mal places: (a) 1 52.73 (b) 1 0.0275 (c) 1 4.92 C 1 1.97 (a) 1 52.73 D 0.01896453 . . . D 0.019, correct to 3 decimal places. (b) 1 0.0275 D 36.3636363 . . . D 36.364, correct to 3 decimal places. (c) 1 4.92 C 1 1.97 D 0.71086624 . . . D 0.711, correct to 3 decimal places. Problem 7. Evaluate the following, expressing the answers in standard form, correct to 4 signiﬁcant ﬁgures. (a) 0.00451 2 (b) 631.7 6.21 C 2.95 2 (c) 46.272 31.792 (a) 0.00451 2 D 2.03401 ð 10 5 D 2.034 U 10−5 , correct to 4 signiﬁcant ﬁgures. (b) 631.7 6.21 C 2.95 2 D 547.7944 D 5.477944 ð 102 D 5.478 U 102 , correct to 4 signiﬁcant ﬁgures. (c) 46.272 31.792 D 1130.3088 D 1.130 U 103 , correct to 4 signiﬁcant ﬁgures. Problem 8. Evaluate the following, correct to 3 deci- mal places: (a) 2.37 2 0.0526 (b) 3.60 1.92 2 C 5.40 2.45 2 (c) 15 7.62 4.82 (a) 2.37 2 0.0526 D 106.785171 . . . D 106.785, correct to 3 decimal places. (b) 3.60 1.92 2 C 5.40 2.45 2 D 8.37360084 . . . D 8.374, correct to 3 decimal places. (c) 15 7.62 4.82 D 0.43202764 . . . D 0.432, correct to 3 decimal places. Problem 9. Evaluate the following, correct to 4 signi- ﬁcant ﬁgures: (a) p 5.462 (b) p 54.62 (c) p 546.2 (a) p 5.462 D 2.3370922 . . . D 2.337, correct to 4 signiﬁ- cant ﬁgures. (b) p 54.62 D 7.39053448 . . . D 7.391, correct to 4 signiﬁ- cant ﬁgures. (c) p 546.2 D 23.370922 . . . D 23.37, correct to 4 signiﬁ- cant ﬁgures. Problem 10. Evaluate the following, correct to 3 dec- imal places: (a) p 0.007328 (b) p 52.91 p 31.76 (c) 1.6291 ð 104 (a) p 0.007328 D 0.08560373 D 0.086, correct to 3 decimal places. (b) p 52.91 p 31.76 D 1.63832491 . . . D 1.638, correct to 3 decimal places. (c) 1.6291 ð 104 D p 16291 D 127.636201 . . . D 127.636, correct to 3 decimal places.
33. 33. Calculations and evaluation of formulae 23 Problem 11. Evaluate the following, correct to 4 sig- niﬁcant ﬁgures: (a) 4.723 (b) 0.8316 4 (c) 76.212 29.102 (a) 4.723 D 105.15404 . . . D 105.2, correct to 4 signiﬁcant ﬁgures. (b) 0.8316 4 D 0.47825324 . . . D 0.4783, correct to 4 signiﬁcant ﬁgures. (c) 76.212 29.102 D 70.4354605 . . . D 70.44, correct to 4 signiﬁcant ﬁgures. Problem 12. Evaluate the following, correct to 3 sig- niﬁcant ﬁgures: (a) 6.092 25.2 ð p 7 (b) 3 p 47.291 (c) 7.2132 C 6.4183 C 3.2914 (a) 6.092 25.2 ð p 7 D 0.74583457 . . . D 0.746, correct to 3 signiﬁcant ﬁgures. (b) 3 p 47.291 D 3.61625876 . . . D 3.62, correct to 3 signiﬁ- cant ﬁgures. (c) 7.2132 C 6.4183 C 3.2914 D 20.8252991 . . . D 20.8, correct to 3 signiﬁcant ﬁgures. Problem 13. Evaluate the following, expressing the answers in standard form, correct to 4 decimal places: (a) 5.176 ð 10 3 2 (b) 1.974 ð 101 ð 8.61 ð 10 2 3.462 4 (c) 1.792 ð 10 4 (a) 5.176ð10 3 2 D 2.679097 . . .ð10 5 D 2.6791 U 10−5 , correct to 4 decimal places. (b) 1.974 ð 101 ð 8.61 ð 10 2 3.462 4 D 0.05808887 . . . D 5.8089 U 10−2 , correct to 4 decimal places (c) 1.792 ð 10 4 D 0.0133865 . . . D 1.3387U 10−2 , correct to 4 decimal places. Now try the following exercise Exercise 13 Further problems on use of calculator (Answers on page 253) In Problems 1 to 3, use a calculator to evaluate the quantities shown correct to 4 signiﬁcant ﬁgures: 1. (a) 3.2492 (b) 73.782 (c) 311.42 (d) 0.06392 2. (a) p 4.735 (b) p 35.46 (c) p 73280 (d) p 0.0256 3. (a) 1 7.768 (b) 1 48.46 (c) 1 0.0816 (d) 1 1.118 In Problems 4 to 11, use a calculator to evaluate correct to 4 signiﬁcant ﬁgures: 4. (a) 43.27 ð 12.91 (b) 54.31 ð 0.5724 5. (a) 127.8 ð 0.0431 ð 19.8 (b) 15.76 ł 4.329 6. (a) 137.6 552.9 (b) 11.82 ð 1.736 0.041 7. (a) 1 17.31 (b) 1 0.0346 (c) 1 147.9 8. (a) 13.63 (b) 3.4764 (c) 0.1245 9. (a) p 347.1 (b) p 7632 (c) p 0.027 (d) p 0.004168 10. (a) 24.68 ð 0.0532 7.412 3 (b) 0.2681 ð 41.22 32.6 ð 11.89 4 11. (a) 14.323 21.682 (b) 4.8213 17.332 15.86 ð 11.6 12. Evaluate correct to 3 decimal places: (a) 29.12 5.81 2 2.96 2 (b) p 53.98 p 21.78 13. Evaluate correct to 4 signiﬁcant ﬁgures: (a) 15.62 2 29.21 ð p 10.52 (b) 6.9212 C 4.8163 2.1614 14. Evaluate the following, expressing the answers in standard form, correct to 3 decimal places: (a) 8.291 ð 10 2 2 (b) 7.623 ð 10 3
34. 34. 24 Basic Engineering Mathematics 4.3 Conversion tables and charts It is often necessary to make calculations from various conversion tables and charts. Examples include currency exchange rates, imperial to metric unit conversions, train or bus timetables, production schedules and so on. Problem 14. Currency exchange rates for ﬁve coun- tries are shown in Table 4.1 Table 4.1 France £1 D 1.50 euros Japan £1 D 175 yen Norway £1 D 11.25 kronor Switzerland £1 D 2.20 francs U.S.A. £1 D 1.52 dollars (\$) Calculate: (a) how many French euros £27.80 will buy, (b) the number of Japanese yen which can be bought for £23, (c) the pounds sterling which can be exchanged for 6412.5 Norwegian kronor, (d) the number of American dollars which can be purchased for £90, and (e) the pounds sterling which can be exchanged for 2794 Swiss francs. (a) £1 D 1.50 euros, hence £27.80 D 27.80 ð 1.50 euros D 41.70 euros (b) £1 D 175 yen, hence £23 D 23 ð 175 yen D 4025 yen (c) £1 D 11.25 kronor, hence 6412.5 kronor D £ 6412.5 11.25 D £570 (d) £1 D 1.52 dollars, hence £90 D 90 ð 1.52 dollars D \$136.80 (e) £1 D 2.20 Swiss francs, hence 2794 franc D £ 2794 2.20 D £1270 Problem 15. Some approximate imperial to metric conversions are shown in Table 4.2 Table 4.2 length 1 inch D 2.54 cm 1 mile D 1.61 km weight 2.2 lb D 1 kg 1 lb D 16 oz capacity 1.76 pints D 1 litre 8 pints D 1 gallon Use the table to determine: (a) the number of millimetres in 9.5 inches, (b) a speed of 50 miles per hour in kilometres per hour, (c) the number of miles in 300 km, (d) the number of kilograms in 30 pounds weight, (e) the number of pounds and ounces in 42 kilograms (correct to the nearest ounce), (f) the number of litres in 15 gallons, and (g) the number of gallons in 40 litres. (a) 9.5 inches D 9.5 ð 2.54 cm D 24.13 cm 24.13 cm D 24.13 ð 10 mm D 241.3 mm (b) 50 m.p.h. D 50 ð 1.61 km/h D 80.5 km=h (c) 300 km D 300 1.61 miles D 186.3 miles (d) 30 lb D 30 2.2 kg D 13.64 kg (e) 42 kg D 42 ð 2.2 lb D 92.4 lb 0.4 lb D 0.4 ð 16 oz D 6.4 oz D 6 oz, correct to the nearest ounce. Thus 42 kg D 92 lb 6 oz, correct to the nearest ounce. (f) 15 gallons D 15 ð 8 pints D 120 pints 120 pints D 120 1.76 litres D 68.18 litres (g) 40 litres D 40 ð 1.76 pints D 70.4 pints 70.4 pints D 70.4 8 gallons D 8.8 gallons Now try the following exercise Exercise 14 Further problems conversion tables and charts (Answers on page 254) 1. Currency exchange rates listed in a newspaper inclu- ded the following: Italy £1 D 1.52 euro Japan £1 D 180 yen Australia £1 D 2.80 dollars Canada £1 D \$2.35 Sweden £1 D 13.90 kronor Calculate (a) how many Italian euros £32.50 will buy, (b) the number of Canadian dollars that can be pur- chased for £74.80, (c) the pounds sterling which can be exchanged for 14 040 yen, (d) the pounds sterling which can be exchanged for 1751.4 Swedish kronor, and (e) the Australian dollars which can be bought for £55
35. 35. Calculations and evaluation of formulae 25 2. Below is a list of some metric to imperial conversions. Length 2.54 cm D 1 inch 1.61 km D 1 mile Weight 1 kg D 2.2 lb 1 lb D 16 ounces Capacity 1 litre D 1.76 pints 8 pints D 1 gallon Use the list to determine (a) the number of millimetres in 15 inches, (b) a speed of 35 mph in km/h, (c) the number of kilometres in 235 miles, (d) the number of pounds and ounces in 24 kg (correct to the nearest ounce), (e) the number of kilograms in 15 lb, (f) the number of litres in 12 gallons and (g) the number of gallons in 25 litres. 3. Deduce the following information from the BR train timetable shown in Table 4.3: (a) At what time should a man catch a train at Mossley Hill to enable him to be in Manchester Piccadilly by 8.15 a.m.? Table 4.3 Liverpool, Hunt’s Cross and Warrington ! Manchester Reproduced with permission of British Rail
36. 36. 26 Basic Engineering Mathematics (b) A girl leaves Hunts Cross at 8.17 a.m. and travels to Manchester Oxford Road. How long does the journey take. What is the average speed of the journey? (c) A man living at Edge Hill has to be at work at Trafford Park by 8.45 a.m. It takes him 10 minutes to walk to his work from Trafford Park station. What time train should he catch from Edge Hill ? 4.4 Evaluation of formulae The statement v D u C at is said to be a formula for v in terms of u, a and t. v, u, a and t are called symbols. The single term on the left-hand side of the equation, v, is called the subject of the formulae. Provided values are given for all the symbols in a for- mula except one, the remaining symbol can be made the subject of the formula and may be evaluated by using a cal- culator. Problem 16. In an electrical circuit the voltage V is given by Ohm’s law, i.e. V D IR. Find, correct to 4 signiﬁcant ﬁgures, the voltage when I D 5.36 A and R D 14.76 . V D IR D 5.36 14.76 Hence voltage V = 79.11 V, correct to 4 signiﬁcant ﬁgures. Problem 17. The surface area A of a hollow cone is given by A D prl. Determine, correct to 1 decimal place, the surface area when r D 3.0 cm and l D 8.5 cm. A D prl D p 3.0 8.5 cm2 Hence surface area A = 80.1 cm2 , correct to 1 decimal place. Problem 18. Velocity v is given by v D u C at. If u D 9.86 m/s, a D 4.25 m/s2 and t D 6.84 s, ﬁnd v, correct to 3 signiﬁcant ﬁgures. v D u C at D 9.86 C 4.25 6.84 D 9.86 C 29.07 D 38.93 Hence velocity v = 38.9 m=s, correct to 3 signiﬁcant ﬁgures. Problem 19. The area, A, of a circle is given by A D pr2 . Determine the area correct to 2 decimal places, given radius r D 5.23 m. A D pr2 D p 5.23 2 D p 27.3529 Hence area, A = 85.93 m2 , correct to 2 decimal places. Problem 20. The power P watts dissipated in an elec- trical circuit may be expressed by the formula P D V2 R . Evaluate the power, correct to 3 signiﬁcant ﬁgures, given that V D 17.48 V and R D 36.12 . P D V2 R D 17.48 2 36.12 D 305.5504 36.12 Hence power, P = 8.46 W, correct to 3 signiﬁcant ﬁg- ures. Problem 21. The volume V cm3 of a right circular cone is given by V D 1 3 pr2 h. Given that r D 4.321 cm and h D 18.35 cm, ﬁnd the volume, correct to 4 signiﬁcant ﬁgures. V D 1 3 pr2 h D 1 3 p 4.321 2 18.35 D 1 3 p 18.671041 18.35 Hence volume, V = 358.8 cm3 , correct to 4 signiﬁcant ﬁgures. Problem 22. Force F newtons is given by the formula F D Gm1m2 d2 , where m1 and m2 are masses, d their distance apart and G is a constant. Find the value of the force given that G D 6.67 ð 10 11 , m1 D 7.36, m2 D 15.5 and d D 22.6. Express the answer in standard form, correct to 3 signiﬁcant ﬁgures. F D Gm1m2 d2 D 6.67 ð 10 11 7.36 15.5 22.6 2 D 6.67 7.36 15.5 1011 510.76 D 1.490 1011 Hence force F = 1.49 U 10−11 newtons, correct to 3 sig- niﬁcant ﬁgures.
37. 37. Calculations and evaluation of formulae 27 Problem 23. The time of swing t seconds, of a simple pendulum is given by t D 2p l g . Determine the time, correct to 3 decimal places, given that l D 12.0 and g D 9.81 t D 2p l g D 2 p 12.0 9.81 D 2 p p 1.22324159 D 2 p 1.106002527 Hence time t = 6.950 seconds, correct to 3 decimal places. Problem 24. Resistance, R , varies with temperature according to the formula R D R0 1 C at . Evaluate R, correct to 3 signiﬁcant ﬁgures, given R0 D 14.59, a D 0.0043 and t D 80. R D R0 1 C at D 14.59[1 C 0.0043 80 ] D 14.59 1 C 0.344 D 14.59 1.344 Hence resistance, R = 19.6 Z, correct to 3 signiﬁcant ﬁgures. Now try the following exercise Exercise 15 Further problems on evaluation of for- mulae (Answers on page 254) 1. The area A of a rectangle is given by the formula A D lb. Evaluate the area when l D 12.4 cm and b D 5.37 cm. 2. The circumference C of a circle is given by the formula C D 2pr. Determine the circumference given p D 3.14 and r D 8.40 mm. 3. A formula used in connection with gases is R D PV /T. Evaluate R when P D 1500, V D 5 and T D 200. 4. The velocity of a body is given by v D u C at. The initial velocity u is measured when time t is 15 seconds and found to be 12 m/s. If the acceleration a is 9.81 m/s2 calculate the ﬁnal velocity v. 5. Calculate the current I in an electrical circuit, when I D V/R amperes when the voltage V is measured and found to be 7.2 V and the resistance R is 17.7 . 6. Find the distance s, given that s D 1 2 gt2 . Time t D 0.032 seconds and acceleration due to gravity g D 9.81 m/s2 . 7. The energy stored in a capacitor is given by E D 1 2 CV2 joules. Determine the energy when capac- itance C D 5 ð 10 6 farads and voltage V D 240 V. 8. Find the area A of a triangle, given A D 1 2 bh, when the base length b is 23.42 m and the height h is 53.7 m. 9. Resistance R2 is given by R2 D R1 1 C at . Find R2, correct to 4 signiﬁcant ﬁgures, when R1 D 220, a D 0.00027 and t D 75.6 10. Density D mass volume . Find the density when the mass is 2.462 kg and the volume is 173 cm3 . Give the answer in units of kg/m3 . 11. Velocity D frequencyðwavelength. Find the velocity when the frequency is 1825 Hz and the wavelength is 0.154 m. 12. Evaluate resistance RT, given 1 RT D 1 R1 C 1 R2 C 1 R3 when R1 D 5.5 , R2 D 7.42 and R3 D 12.6 . 13. Find the total cost of 37 calculators costing £12.65 each and 19 drawing sets costing £6.38 each. 14. Power D force ð distance time . Find the power when a force of 3760 N raises an object a distance of 4.73 m in 35 s. 15. The potential difference, V volts, available at battery terminals is given by V D E Ir. Evaluate V when E D 5.62, I D 0.70 and R D 4.30 16. Given force F D 1 2 m v2 u2 , ﬁnd F when m D 18.3, v D 12.7 and u D 8.24 17. The current I amperes ﬂowing in a number of cells is given by I D nE R C nr . Evaluate the current when n D 36, E D 2.20, R D 2.80 and r D 0.50 18. The time, t seconds, of oscillation for a simple pendulum is given by t D 2p l g . Determine the time when p D 3.142, l D 54.32 and g D 9.81 19. Energy, E joules, is given by the formula E D 1 2 LI2 . Evaluate the energy when L D 5.5 and I D 1.2 20. The current I amperes in an a.c. circuit is given by I D V R2 C X2 . Evaluate the current when V D 250, R D 11.0 and X D 16.2 21. Distance s metres is given by the formula s D ut C 1 2 at2 . If u D 9.50, t D 4.60 and a D 2.50, evaluate the distance.
38. 38. 28 Basic Engineering Mathematics 22. The area, A, of any triangle is given by A D p [s s a s b s c ] where s D a C b C c 2 . Evaluate the area given a D 3.60 cm, b D 4.00 cm and c D 5.20 cm. 23. Given that a D 0.290, b D 14.86, c D 0.042, d D 31.8 and e D 0.650, evaluate v given that v D ab c d e Assignment 2 This assignment covers the material contained in Chapters 3 and 4. The marks for each question are shown in brackets at the end of each question. 1. Evaluate the following: (a) 23 ð 2 ð 22 24 (b) 23 ð 16 2 8 ð 2 3 (c) 1 42 1 (d) 27 1/3 (e) 3 2 2 2 9 2 3 2 (14) 2. Express the following in standard form: (a) 1623 (b) 0.076 (c) 1452 5 (6) 3. Determine the value of the following, giving the answer in standard form: (a) 5.9 ð 102 C 7.31 ð 102 (b) 2.75 ð 10 2 2.65 ð 10 3 (6) 4. Is the statement 73 ð 0.009 15.7 D 4.18ð10 2 correct? If not, what should it be? (2) 5. Evaluate the following, each correct to 4 signiﬁcant ﬁgures: (a) 61.222 (b) 1 0.0419 (c) p 0.0527 (6) 6. Evaluate the following, each correct to 2 decimal places: (a) 36.22 ð 0.561 27.8 ð 12.83 3 (b) 14.692 p 17.42 ð 37.98 (7) 7. If 1.6 km D 1 mile, determine the speed of 45 miles/hour in kilometres per hour. (3) 8. The area A of a circle is given by A D pr2 . Find the area of a circle of radius r D 3.73 cm, correct to 2 decimal places. (3) 9. Evaluate B, correct to 3 signiﬁcant ﬁgures, when W D 7.20, v D 10.0 and g D 9.81, given that B D Wv2 2g (3)
39. 39. 5 Computer numbering systems 5.1 Binary numbers The system of numbers in everyday use is the denary or decimal system of numbers, using the digits 0 to 9. It has ten different digits (0, 1, 2, 3, 4, 5, 6, 7, 8 and 9) and is said to have a radix or base of 10. The binary system of numbers has a radix of 2 and uses only the digits 0 and 1. 5.2 Conversion of binary to denary The denary number 234.5 is equivalent to 2 ð 102 C 3 ð 101 C 4 ð 100 C 5 ð 10 1 i.e. is the sum of terms comprising: (a digit) multiplied by (the base raised to some power). In the binary system of numbers, the base is 2, so 1101.1 is equivalent to: 1 ð 23 C 1 ð 22 C 0 ð 21 C 1 ð 20 C 1 ð 2 1 Thus the denary number equivalent to the binary number 1101.1 is 8 C 4 C 0 C 1 C 1 2 , that is 13.5 i.e. 1101.12 = 13.510, the sufﬁxes 2 and 10 denoting binary and denary systems of numbers respectively. Problem 1. Convert 110112 to a denary number. From above: 110112 D 1 ð 24 C 1 ð 23 C 0 ð 22 C 1 ð 21 C 1 ð 20 D 16 C 8 C 0 C 2 C 1 D 2710 Problem 2. Convert 0.10112 to a decimal fraction. 0.10112 D 1 ð 2 1 C 0 ð 2 2 C 1 ð 2 3 C 1 ð 2 4 D 1 ð 1 2 C 0 ð 1 22 C 1 ð 1 23 C 1 ð 1 24 D 1 2 C 1 8 C 1 16 D 0.5 C 0.125 C 0.0625 D 0.687510 Problem 3. Convert 101.01012 to a denary number. 101.01012 D 1 ð 22 C 0 ð 21 C 1 ð 20 C 0 ð 2 1 C 1 ð 2 2 C 0 ð 2 3 C 1 ð 2 4 D 4 C 0 C 1 C 0 C 0.25 C 0 C 0.0625 D 5.312510 Now try the following exercise Exercise 16 Further problems on conversion of bi- nary to denary numbers (Answers on page 254) In Problems 1 to 4, convert the binary numbers given to denary numbers. 1. (a) 110 (b) 1011 (c) 1110 (d) 1001 2. (a) 10101 (b) 11001 (c) 101101 (d) 110011
40. 40. 30 Basic Engineering Mathematics 3. (a) 0.1101 (b) 0.11001 (c) 0.00111 (d) 0.01011 4. (a) 11010.11 (b) 10111.011 (c) 110101.0111 (d) 11010101.10111 5.3 Conversion of denary to binary An integer denary number can be converted to a correspond- ing binary number by repeatedly dividing by 2 and noting the remainder at each stage, as shown below for 3910 0 1 1 0 0 1 1 1 2 39 Remainder 2 19 1 2 9 1 2 4 1 2 2 0 2 1 0 (most significant bit)→ ←(least significant bit) The result is obtained by writing the top digit of the remain- der as the least signiﬁcant bit, (a bit is a binary digit and the least signiﬁcant bit is the one on the right). The bottom bit of the remainder is the most signiﬁcant bit, i.e. the bit on the left. Thus 3910 = 1001112 The fractional part of a denary number can be converted to a binary number by repeatedly multiplying by 2, as shown below for the fraction 0.625 0.625 × 2 D 1. 250 0.250 × 2 D 0. 500 0.500 × 2 D 1. 000 11 0.(most significant bit) (least significant bit) For fractions, the most signiﬁcant bit of the result is the top bit obtained from the integer part of multiplication by 2. The least signiﬁcant bit of the result is the bottom bit obtained from the integer part of multiplication by 2. Thus 0.62510 = 0.1012 Problem 4. Convert 4710 to a binary number. From above, repeatedly dividing by 2 and noting the remain- der gives: 2 47 Remainder 2 23 1 2 11 1 2 5 1 2 2 1 2 1 0 0 1 1 0 1 1 11 Thus 4710 = 1011112 Problem 5. Convert 0.4062510 to a binary number. From above, repeatedly multiplying by 2 gives: 0.40625 × 2 D 0. 8125 0.8125 × 2 D 1. 625 0.625 × 2 D 1. 25 0.25 × 2 D 0. 5 0.5 × 2 D 1. 0 . 0 1 1 0 1 i.e. 0.4062510 = 0.011012 Problem 6. Convert 58.312510 to a binary number. The integer part is repeatedly divided by 2, giving: 2 58 Remainder 2 29 0 2 14 1 2 7 0 2 3 1 2 1 1 0 1 1 1 1 1 00
41. 41. Computer numbering systems 31 The fractional part is repeatedly multiplied by 2 giving: 0.3125 × 2 D 0.625 0.625 × 2 D 1.25 0.25 × 2 D 0.5 0.5 × 2 D 1.0 . 0 1 0 1 Thus 58.312510 = 111010.01012 Now try the following exercise Exercise 17 Further problems on conversion of de- nary to binary numbers (Answers on page 254) In Problems 1 to 4, convert the denary numbers given to binary numbers. 1. (a) 5 (b) 15 (c) 19 (d) 29 2. (a) 31 (b) 42 (c) 57 (d) 63 3. (a) 0.25 (b) 0.21875 (c) 0.28125 (d) 0.59375 4. (a) 47.40625 (b) 30.8125 (c) 53.90625 (d) 61.65625 5.4 Conversion of denary to binary via octal For denary integers containing several digits, repeatedly dividing by 2 can be a lengthy process. In this case, it is usually easier to convert a denary number to a binary number via the octal system of numbers. This system has a radix of 8, using the digits 0, 1, 2, 3, 4, 5, 6 and 7. The denary number equivalent to the octal number 43178 is 4 ð 83 C 3 ð 82 C 1 ð 81 C 7 ð 80 i.e. 4 ð 512 C 3 ð 64 C 1 ð 8 C 7 ð 1 or 225510 An integer denary number can be converted to a correspond- ing octal number by repeatedly dividing by 8 and noting the remainder at each stage, as shown below for 49310 8 493 Remainder 8 61 5 8 7 5 0 7 7 5 5 Thus 49310 D 7558 The fractional part of a denary number can be converted to an octal number by repeatedly multiplying by 8, as shown below for the fraction 0.437510 0.4375 × 8 D 3 . 5 0.5 × 8 D . 3 4 4 . 0 For fractions, the most signiﬁcant bit is the top integer obtained by multiplication of the denary fraction by 8, thus 0.437510 D 0.348 The natural binary code for digits 0 to 7 is shown in Table 5.1, and an octal number can be converted to a binary number by writing down the three bits corresponding to the octal digit. Table 5.1 Octal digit Natural binary number 0 000 1 001 2 010 3 011 4 100 5 101 6 110 7 111 Thus 4378 D 100 011 1112 and 26.358 D 010 110.011 1012 The ‘0’ on the extreme left does not signify anything, thus 26.358 D 10 110.011 1012 Conversion of denary to binary via octal is demonstrated in the following worked problems. Problem 7. Convert 371410 to a binary number, via octal. Dividing repeatedly by 8, and noting the remainder gives: 8 58 0 0 7 7 2 0 2 8 3714 Remainder 8 464 2 8 7 2
42. 42. 32 Basic Engineering Mathematics From Table 5.1, 72028 D 111 010 000 0102 i.e. 371410 = 111 010 000 0102 Problem 8. Convert 0.5937510 to a binary number, via octal. Multiplying repeatedly by 8, and noting the integer values, gives: 0.59375 × 8 D 4.75 0.75 × 8 D 6.00 . 4 6 Thus 0.5937510 D 0.468 From Table 5.1, 0.468 D 0.100 1102 i.e. 0.5937510 = 0.100 112 Problem 9. Convert 5613.9062510 to a binary number, via octal. The integer part is repeatedly divided by 8, noting the remainder, giving: 8 5613 Remainder 8 701 5 8 8 87 5 10 8 1 0 7 2 1 2 7 5 51 This octal number is converted to a binary number, (see Table 5.1) 127558 D 001 010 111 101 1012 i.e. 561310 D 1 010 111 101 1012 The fractional part is repeatedly multiplied by 8, and noting the integer part, giving: 0.90625 × 8 D 7.25 0.25 × 8 D 2.00 . 7 2 This octal fraction is converted to a binary number, (see Table 5.1) 0.728 D 0.111 0102 i.e. 0.9062510 D 0.111 012 Thus, 5613.9062510 = 1 010 111 101 101.111 012 Problem 10. Convert 11 110 011.100 012 to a denary number via octal. Grouping the binary number in three’s from the binary point gives: 011 110 011.100 0102 Using Table 5.1 to convert this binary number to an octal number gives: 363.428 and 363.428 D 3 ð 82 C 6 ð 81 C 3 ð 80 C 4 ð 8 1 C 2 ð 8 2 D 192 C 48 C 3 C 0.5 C 0.03125 D 243.5312510 Now try the following exercise Exercise 18 Further problems on conversion bet- ween denary and binary numbers via octal (Answers on page 254) In Problems 1 to 3, convert the denary numbers given to binary numbers, via octal. 1. (a) 343 (b) 572 (c) 1265 2. (a) 0.46875 (b) 0.6875 (c) 0.71875 3. (a) 247.09375 (b) 514.4375 (c) 1716.78125 4. Convert the following binary numbers to denary num- bers via octal: (a) 111.011 1 (b) 101 001.01 (c) 1 110 011 011 010.001 1 5.5 Hexadecimal numbers The complexity of computers requires higher order number- ing systems such as octal (base 8) and hexadecimal (base 16) which are merely extensions of the binary system. A hexadecimal numbering system has a radix of 16 and uses the following 16 distinct digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E and F ‘A’ corresponds to 10 in the denary system, B to 11, C to 12, and so on. To convert from hexadecimal to decimal: For example 1A16 D 1 ð 161 C A ð 160 D 1 ð 161 C 10 ð 1 D 16 C 10 D 26 i.e. 1A16 D 2610 Similarly, 2E16 D 2 ð 161 C E ð 160 D 2 ð 161 C 14 ð 160 D 32 C 14 D 4610
43. 43. Computer numbering systems 33 and 1BF16 D 1 ð 162 C B ð 161 C F ð 160 D 1 ð 162 C 11 ð 161 C 15 ð 160 D 256 C 176 C 15 D 44710 Table 5.2 compares decimal, binary, octal and hexadecimal numbers and shows, for example, that 2310 D 101112 D 278 D 1716 Table 5.2 Decimal Binary Octal Hexadecimal 0 0000 0 0 1 0001 1 1 2 0010 2 2 3 0011 3 3 4 0100 4 4 5 0101 5 5 6 0110 6 6 7 0111 7 7 8 1000 10 8 9 1001 11 9 10 1010 12 A 11 1011 13 B 12 1100 14 C 13 1101 15 D 14 1110 16 E 15 1111 17 F 16 10000 20 10 17 10001 21 11 18 10010 22 12 19 10011 23 13 20 10100 24 14 21 10101 25 15 22 10110 26 16 23 10111 27 17 24 11000 30 18 25 11001 31 19 26 11010 32 1A 27 11011 33 1B 28 11100 34 1C 29 11101 35 1D 30 11110 36 1E 31 11111 37 1F 32 100000 40 20 Problem 11. Convert the following hexadecimal num- bers into their decimal equivalents: (a) 7A16 (b) 3F16 (a) 7A16 D 7 ð 161 C A ð 160 D 7 ð 16 C 10 ð 1 D 112 C 10 D 122 Thus 7A16 = 12210 (b) 3F16 D 3 ð 161 C F ð 160 D 3 ð 16 C 15 ð 1 D 48 C 15 D 63 Thus 3F16 = 6310 Problem 12. Convert the following hexadecimal num- bers into their decimal equivalents: (a) C916 (b) BD16 (a) C916 D C ð 161 C 9 ð 160 D 12 ð 16 C 9 ð 1 D 192 C 9 D 201 Thus C916 = 20110 (b) BD16 D B ð 161 C D ð 160 D 11 ð 16 C 13 ð 1 D 176 C 13 D 189 Thus BD16 = 18910 Problem 13. Convert 1A4E16 into a denary number. 1A4E16 D 1 ð 163 C A ð 162 C 4 ð 161 C E ð 160 D 1 ð 163 C 10 ð 162 C 4 ð 161 C 14 ð 160 D 1 ð 4096 C 10 ð 256 C 4 ð 16 C 14 ð 1 D 4096 C 2560 C 64 C 14 D 6734 Thus 1A4E16 = 673410 To convert from decimal to hexadecimal: This is achieved by repeatedly dividing by 16 and noting the remainder at each stage, as shown below for 2610 0 1 ≡ 116 most significant bit → 1 A ← least significant bit 16 ≡ A16101 16 Remainder26 Hence 2610 = 1A16 Similarly, for 44710 16 16 ≡ B16 0 ≡ 1161 1 B F 11 16 ≡ F16 Remainder 15 447 27 1 Thus 44710 = 1BF16