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# Stdform

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### Stdform

1. 1. Form 4 Chapter 1 : Standard Form
2. 2. 1.1 Significant figure  All zeros between non-zero digits are significant figures (s.f). Eg: 2008 [4 s.f] 506.07 [5 s.f.]  All zeros at the end of a decimal are s.f. Eg: 2.60 [3 s.f.] 7.1000 [5 s.f.]  All zeros at the end of a whole number are not s.f. unless stated otherwise. Eg : 1000 [1 s.f.] 1000 [2 s.f.] 1000 [3 s.f.] 1000 [4 s.f.]  Number < 1 All zeros on the left-hand side of a non-zero digit are not s.f. Eg: 0.168 [3 s.f.] 0.00068 [2 s.f.]
3. 3. Try this exercise :  State the number of significant figures. a) 438 b) 40308 c) 7.060 d) 0.000078 e) 0.508 Answer : a) 3 b) 5 c) 4 d) 2 e) 3
4. 4. 1.1 a : Rounding off numbers Do the digits after x lie before or after the decimal point ? Identify the digit (x) that is to be rounded off No x remains unchanged Add 1 to x Is the digit after x greater than or equal to 5 ? Replace each digit with a zero. Drop the digits. Before After Yes
5. 5. Example : Eg 1 : Round off 57.63 to : a) 3 significant figures. b) 1 significant figure. Answer : a) 57.6 b) 60 Eg 2 : Round off 0.002035 to : a) 3 significant figures. b) 1 significant figure. Answer : a) 0.00204 b) 0.002
6. 6. 1.2 Standard Form Numbers written in the form : A × 10n where 1 ≤ A ≤ 10 and n is an integer.  n is positive for numbers ≥ 10  n is negative for numbers ≤ 1
7. 7. 1.2 a: Expressing positive numbers in standard form  Express the following numbers in standard form. a) 1688 b) 290000 c) 0.035 d) 0.000123 Answer: a) 1.688 x 103 b) 2.9 x 105 c) 3.5 x 10 -2 d) 1.23 x 10- 4
8. 8. 1.2b : Converting standard form to single numbers  Convert the following numbers in standard form to a single number. a) 5.43 x 105 b) 6.493 x 10- 3 c) 1.2345 x 10- 3 Answer: a) 543 000 b) 0.006493 c) 0.0012345