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# Maths A - Skill sheets

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### Maths A - Skill sheets

1. 1. SkillSHEET answers SkillSHEET 1.1 Percentages To ﬁnd a certain percentage of a quantity, change the percentage into a fraction or a decimal and multiply by that quantity. To increase or decrease some amount by a certain percentage is a calculation which is often required. An increase yields a larger number and a decrease yields a smaller number compared with the original value. To increase a number by r%, multiply the number by (1 + ); to decrease a number by r% multiply by (1 – ). The number (1 + ) or (1 – ) is often referred to as the multiplying factor. Try these 1 Find: a 10% of 60 b 5% of 130 c 40% of \$800 d 25% of 700 students e 16% of 75 f 53% of \$20 g 4% of 132 h 7.5% of 260 articles. 2 If 95% of students passed their mid-year examination, how many of the 140 students passed? 3 Enrolments this year increased by 12% from last year. If there were 510 enrolments recorded last year, what is the total recorded enrolment for this year ? 4 a Wages will be increased by r%. What is the multiplying factor if wages increased by: i 10% ii 20% iii 25% iv 7% v 12 %? b If a person is earning \$260 per week, calculate the new wage if it increased by: i 10% ii 20% iii 25% iv 7% v 12 %. 5 a The price of an item is reduced by r%. What is the multiplying factor if the reduction was: i 10% ii 20% iii 25% iv 7% v 12 %? b If the printer cost \$360, calculate its value if the initial cost depreciated by: i 10% ii 20% iii 25% iv 7% v 12 %. Find 15% of \$270. Solution Express 15% as a fraction and multiply by 270. 15% of \$270 = × = = \$ 40.50 15 100 --------- 270 1 --------- 4050 100 ------------ WORKEDExample 1 r 100 --------- r 100 --------- r 100 --------- r 100 --------- Increase \$50 by 15%. Decrease 340 by 5%. Solution Solution To increase by 15%, multiply \$50 by (1 + ). 50 × (1 + ) = 50 × (1 + 0.15) = 50 × 1.15 = \$57.50 To decrease by 5%, multiply 340 by (1 − ). 340 × (1 − ) = 340 × (1 − 0.95) = 340 × 0.95 = 323 15 100 --------- 15 100 --------- 5 100 --------- 5 100 --------- 2WORKEDExample 3WORKEDExample 1 2 --- 1 2 --- 1 2 --- 1 2 ---
2. 2. SkillSHEET answers SkillSHEET 1.2 Expressing one number as a percentage of another To express one number as a percentage of another, form a fraction using these two numbers and multiply it by 100. Note that the number that is being expressed as a percentage is placed in the numerator of the fraction. For example, if we need to express 5 as a percentage of 20, we put 5 in the numerator and 20 in the denominator of a fraction (that is, ). Try these For each of the following, express the ﬁrst number as a percentage of the second number, giving your answer correct to two decimal places. 1 42, 53 2 13, 75 3 34, 150 4 47, 95 5 3, 21 6 12, 35 7 23, 60 8 256, 780 9 7, 65 10 5, 41 11 12, 28 12 37, 61 13 341, 730 14 11, 25 15 15, 24 5 20 ------ Express 18 as a percentage of 34. Solution Form a fraction by placing 18 in the numerator and 34 in the denominator. To change a fraction into a percentage, multiply by 100. × 100 = × (Write 100 as a fraction by putting it over 1.) = (Multiply numerators together and denominators together.) = 52.94% (Divide the numerator by the denominator, giving the answer correct to two decimal places.) 18 34 ------ 18 34 ------ 18 34 ------ 100 1 --------- 1800 34 ------------ WORKEDExample
3. 3. SkillSHEET answers SkillSHEET 1.3 Ratio A ratio is a comparison of two quantities using the same units. A rate is a comparison of two quantities using different units. For example the concentrate of a pesticide, Xenon, must be diluted before use. The instructions suggest that 15 mL of pesticide be mixed with 750 mL of water. This is written: Pesticide : Water 15 mL : 750 mL. Clearly if one were to mix 5 mL of pesticide with 250 mL of water the strength of the mixture would be the same. The ratio 5 mL : 250 mL is equivalent to 15 mL : 750 mL. The instructions for this pesticide say that 500 mL will cover 20 m2 in area. Because these quantities have dif- ferent units their comparison is called a rate: 500 mL : 20 m2 is a rate which is equivalent to 250 mL : 10 m2 . Alternatively one can write 500 mL per 20 m2 and then reduce it to 25 mL per 1 m2 or 25 mL/m2 . If these ratios are all equivalent to 400 : 600, ﬁnd A car travels 350 km on 24 L of petrol. Simplify this the missing number. rate and calculate how many kilometres the same car a 200 : x will travel on 40 L of fuel. b x : 200 c x : 150 Solution Solution a 400 ÷ 2 = 200, so x = 600 ÷ 2 = 300 b 600 ÷ 3 = 200, so x = 400 ÷ 3 = 133·3 c 600 ÷ 4 = 150, so x = 400 ÷ 4 = 100 The rate is 350 kM per 24 litres = 350/24 km per litre = 14·58 km/L. On 40 L the car will travel 40 × 14·6 km = 583 km. 1WORKEDExample 2WORKEDExample Jan and Dean built a bird-bath which they sold at the markets for \$140. They agreed that Jan had spent 4 hours building it and that Dean had worked for 3 hours. If the money is split in the same ratio as the time they spent, how much does each of them receive? Solution Jan : Dean 4 : 3 Total number of hours = 7 So Jan gets of \$140 = \$80 and Dean gets of \$140 = \$60 4 7 --- 3 7 --- 3WORKEDExample
4. 4. SkillSHEET answers Try these 1 If these ratios are all equivalent to 30 : 48, ﬁnd the missing number. a 120 : x b x : 240 c x : 36 2 If these ratios are all equivalent to 25 : 200, ﬁnd the missing number. a 200 : x b x : 2 c x : 150 3 If a car travels 250 km on 22 L of petrol, express this rate in kilometres per litre and calculate the amount of petrol needed by this car for a journey of 600 km. 4 If a car travels 150 km on 18 L of petrol, express this rate in kilometres per litre and calculate the amount of petrol needed by this car for a journey of 500 km. 5 A weed-killer concentrate should be mixed with water in the ratio of 25 mL to 2000 mL (2 L). If there is only 15 mL of the concentrate remaining, how much water should be mixed with it? 6 Patsy and Crystal set up a screen printing business, with Patsy contributing \$1200 and Crystal \$700. How should the ﬁrst month’s proﬁt of \$400 be distributed? 7 The Green Pines resort charges \$624 per person for a 7-night stay. At the same rate what would you expect to pay for a 2-night stay? 8 To stay 5 nights at the Cool Breeze Caravan Park costs \$47·50. What would you pay for 2 nights at the same rate? 9 A car travels at 80 km/h. Express this rate in these units. a metres/hour b metres/minute c metres/second d hours/100 kilometres 10 Hewey Lewis can run 100 m in 12 s. How fast is this in km/h? 11 The speed of sound is 340 m/s. a What is this speed in km/h? b In the 200-metre event the starting gun is 170 m from the timers. If we assume that the smoke from the gun is seen as soon as the gun is ﬁred, how much of a time lag is there between when the ﬁring is seen and heard by the timers? If a timer were to start his watch on the sound of the gun, would the athletes’ recorded time be faster (lower) or slower (higher)? c For investigation: The speed of sound given here is its speed in air at sea level. How does it change as you go higher?
5. 5. SkillSHEET answers SkillSHEET 2.1 — Finding a percentage of a quantity The most common application of percentages is to ﬁnd a percentage of a quantity. In many cases this will be a percentage of a money amount. To ﬁnd the percentage of an amount, write the percentage as a fraction or a decimal and then multiply by the amount. The simplest way to do this is to divide the percentage by 100, which converts the percentage to a decimal before multiplying. Try these 1 Calculate each of the following. a 25% of \$32 b 50% of \$460 c 75% of \$84 d 4% of \$1400 e 8% of \$520 f 3% of \$624 g 33 % of \$540 h 66 % of \$360 i 12 % of \$400 j % of \$640 k % of \$585 l 6.5% of \$734 2 Ricky works as a clerk and receives \$315.00 per week. He receives a 4% pay rise. How much extra does Ricky receive each week? 3 Sally is an accountant with an annual salary of \$42 000. She receives a Christmas bonus of 3% of her salary. Calculate the size of her Christmas bonus. 4 Mr and Mrs Hamilton sell their house for \$192 000. They must pay a commission to the real estate agent of 2.5%. Calculate the amount of commission received by the real estate agent. 5 Dagmar has shares in a company to the value of \$23 500. The dividend paid to the shareholders is 2.5% of the value of shares held. Calculate the amount Dagmar receives as her dividend. 6 The value of the Australian economy is \$2560 billion. The government announces that the economy will grow by 2.1% over the next year. Calculate the amount by which the government predicts the economy to grow. Find 48% of \$380. THINK WRITE Divide 48 by 100 and then multiply by \$380. 48% of \$380 = 48 ÷ 100 × \$380 = \$182.40 WORKEDExample 1 3 --- 2 3 --- 1 2 --- 1 2 --- 3 4 ---
6. 6. SkillSHEET answers SkillSHEET 2.2 — Increase or decrease by a percentage When asked to increase by a percentage, add the percentage to 100% before ﬁnding the total percentage of the quantity. If decreasing by a percentage the method is similar, except subtract the percentage from 100%. Try these 1 Calculate each of the following. a Increase \$380 by 5%. b Increase \$850 by 12%. c Increase \$85 by 65%. d Increase \$750 by 2.5%. 2 Calculate each of the following. a Decrease \$150 by 5%. b Decrease \$386 by 40%. c Decrease \$1250 by 90%. d Decrease \$75 by 1%. 3 A drill set sells at the hardware store for \$136.00. The price is then increased by 8%. Calculate the new price of the drill set. 4 A motel room is advertised at \$120 per night. A 12% surcharge is added on weekends. Calculate the cost per night of the motel on weekends. 5 Kristan receives \$430 per week in her part-time job as a journalist. She pays 25% of this in tax. Calculate the amount of money that Kristan has left in her pay packet after tax has been deducted. 6 The cost of a restaurant bill has been reduced by 7.5% due to poor service. If the original bill was \$98.50, cal- culate the amount to be paid. A sports store buys softball bats for \$35 each and the mark-up on each bat is 40%. Calculate the selling price of the softball bats. THINK WRITE Add 40% to 100% to ﬁnd the percentage that we are ﬁnding of \$35. 140% of \$35 Divide 140 by 100 and then multiply by \$35. = 140 ÷ 100 × \$35 = \$49 Give a written answer. The softball bats sell for \$49 each. 1 2 3 WORKEDExample
7. 7. SkillSHEET answers SkillSHEET 2.3 Ratio A ratio is a comparison of two quantities using the same units. A rate is a comparison of two quantities using different units. For example the concentrate of a pesticide, Xenon, must be diluted before use. The instructions suggest that 15 mL of pesticide be mixed with 750 mL of water. This is written: Pesticide : Water 15 mL : 750 mL. Clearly if one were to mix 5 mL of pesticide with 250 mL of water the strength of the mixture would be the same. The ratio 5 mL : 250 mL is equivalent to 15 mL : 750 mL. The instructions for this pesticide say that 500 mL will cover 20 m2 in area. Because these quantities have dif- ferent units their comparison is called a rate: 500 mL : 20 m2 is a rate which is equivalent to 250 mL : 10 m2 . Alternatively one can write 500 mL per 20 m2 and then reduce it to 25 mL per 1 m2 or 25 mL/m2 . If these ratios are all equivalent to 400 : 600, ﬁnd A car travels 350 km on 24 L of petrol. Simplify this the missing number. rate and calculate how many kilometres the same car a 200 : x will travel on 40 L of fuel. b x : 200 c x : 150 Solution Solution a 400 ÷ 2 = 200, so x = 600 ÷ 2 = 300 b 600 ÷ 3 = 200, so x = 400 ÷ 3 = 133·3 c 600 ÷ 4 = 150, so x = 400 ÷ 4 = 100 The rate is 350 kM per 24 litres = 350/24 km per litre = 14·58 km/L. On 40 L the car will travel 40 × 14·6 km = 583 km. 1WORKEDExample 2WORKEDExample Jan and Dean built a bird-bath which they sold at the markets for \$140. They agreed that Jan had spent 4 hours building it and that Dean had worked for 3 hours. If the money is split in the same ratio as the time they spent, how much does each of them receive? Solution Jan : Dean 4 : 3 Total number of hours = 7 So Jan gets of \$140 = \$80 and Dean gets of \$140 = \$60 4 7 --- 3 7 --- 3WORKEDExample
8. 8. SkillSHEET answers Try these 1 If these ratios are all equivalent to 30 : 48, ﬁnd the missing number. a 120 : x b x : 240 c x : 36 2 If these ratios are all equivalent to 25 : 200, ﬁnd the missing number. a 200 : x b x : 2 c x : 150 3 If a car travels 250 km on 22 L of petrol, express this rate in kilometres per litre and calculate the amount of petrol needed by this car for a journey of 600 km. 4 If a car travels 150 km on 18 L of petrol, express this rate in kilometres per litre and calculate the amount of petrol needed by this car for a journey of 500 km. 5 A weed-killer concentrate should be mixed with water in the ratio of 25 mL to 2000 mL (2 L). If there is only 15 mL of the concentrate remaining, how much water should be mixed with it? 6 Patsy and Crystal set up a screen printing business, with Patsy contributing \$1200 and Crystal \$700. How should the ﬁrst month’s proﬁt of \$400 be distributed? 7 The Green Pines resort charges \$624 per person for a 7-night stay. At the same rate what would you expect to pay for a 2-night stay? 8 To stay 5 nights at the Cool Breeze Caravan Park costs \$47·50. What would you pay for 2 nights at the same rate? 9 A car travels at 80 km/h. Express this rate in these units. a metres/hour b metres/minute c metres/second d hours/100 kilometres 10 Hewey Lewis can run 100 m in 12 s. How fast is this in km/h? 11 The speed of sound is 340 m/s. a What is this speed in km/h? b In the 200-metre event the starting gun is 170 m from the timers. If we assume that the smoke from the gun is seen as soon as the gun is ﬁred, how much of a time lag is there between when the ﬁring is seen and heard by the timers? If a timer were to start his watch on the sound of the gun, would the athletes’ recorded time be faster (lower) or slower (higher)? c For investigation: The speed of sound given here is its speed in air at sea level. How does it change as you go higher?
9. 9. SkillSHEET answers SkillSHEET 3.1 — Finding a percentage of a quantity The most common application of percentages is to ﬁnd a percentage of a quantity. In many cases this will be a percentage of a money amount. To ﬁnd the percentage of an amount, write the percentage as a fraction or a decimal and then multiply by the amount. The simplest way to do this is to divide the percentage by 100, which converts the percentage to a decimal before multiplying. Try these 1 Calculate each of the following. a 25% of \$32 b 50% of \$460 c 75% of \$84 d 4% of \$1400 e 8% of \$520 f 3% of \$624 g 33 % of \$540 h 66 % of \$360 i 12 % of \$400 j % of \$640 k % of \$585 l 6.5% of \$734 2 Ricky works as a clerk and receives \$315.00 per week. He receives a 4% pay rise. How much extra does Ricky receive each week? 3 Sally is an accountant with an annual salary of \$42 000. She receives a Christmas bonus of 3% of her salary. Calculate the size of her Christmas bonus. 4 Mr and Mrs Hamilton sell their house for \$192 000. They must pay a commission to the real estate agent of 2.5%. Calculate the amount of commission received by the real estate agent. 5 Dagmar has shares in a company to the value of \$23 500. The dividend paid to the shareholders is 2.5% of the value of shares held. Calculate the amount Dagmar receives as her dividend. 6 The value of the Australian economy is \$2560 billion. The government announces that the economy will grow by 2.1% over the next year. Calculate the amount by which the government predicts the economy to grow. Find 48% of \$380. THINK WRITE Divide 48 by 100 and then multiply by \$380. 48% of \$380 = 48 ÷ 100 × \$380 = \$182.40 WORKEDExample 1 3 --- 2 3 --- 1 2 --- 1 2 --- 3 4 ---
10. 10. SkillSHEET answers SkillSHEET 3.2 — Increase or decrease by a percentage When asked to increase by a percentage, add the percentage to 100% before ﬁnding the total percentage of the quantity. If decreasing by a percentage the method is similar, except subtract the percentage from 100%. Try these 1 Calculate each of the following. a Increase \$380 by 5%. b Increase \$850 by 12%. c Increase \$85 by 65%. d Increase \$750 by 2.5%. 2 Calculate each of the following. a Decrease \$150 by 5%. b Decrease \$386 by 40%. c Decrease \$1250 by 90%. d Decrease \$75 by 1%. 3 A drill set sells at the hardware store for \$136.00. The price is then increased by 8%. Calculate the new price of the drill set. 4 A motel room is advertised at \$120 per night. A 12% surcharge is added on weekends. Calculate the cost per night of the motel on weekends. 5 Kristan receives \$430 per week in her part-time job as a journalist. She pays 25% of this in tax. Calculate the amount of money that Kristan has left in her pay packet after tax has been deducted. 6 The cost of a restaurant bill has been reduced by 7.5% due to poor service. If the original bill was \$98.50, cal- culate the amount to be paid. A sports store buys softball bats for \$35 each and the mark-up on each bat is 40%. Calculate the selling price of the softball bats. THINK WRITE Add 40% to 100% to ﬁnd the percentage that we are ﬁnding of \$35. 140% of \$35 Divide 140 by 100 and then multiply by \$35. = 140 ÷ 100 × \$35 = \$49 Give a written answer. The softball bats sell for \$49 each. 1 2 3 WORKEDExample
11. 11. SkillSHEET answers SkillSHEET 3.3 Ratio A ratio is a comparison of two quantities using the same units. A rate is a comparison of two quantities using different units. For example the concentrate of a pesticide, Xenon, must be diluted before use. The instructions suggest that 15 mL of pesticide be mixed with 750 mL of water. This is written: Pesticide : Water 15 mL : 750 mL. Clearly if one were to mix 5 mL of pesticide with 250 mL of water the strength of the mixture would be the same. The ratio 5 mL : 250 mL is equivalent to 15 mL : 750 mL. The instructions for this pesticide say that 500 mL will cover 20 m2 in area. Because these quantities have dif- ferent units their comparison is called a rate: 500 mL : 20 m2 is a rate which is equivalent to 250 mL : 10 m2 . Alternatively one can write 500 mL per 20 m2 and then reduce it to 25 mL per 1 m2 or 25 mL/m2 . If these ratios are all equivalent to 400 : 600, ﬁnd A car travels 350 km on 24 L of petrol. Simplify this the missing number. rate and calculate how many kilometres the same car a 200 : x will travel on 40 L of fuel. b x : 200 c x : 150 Solution Solution a 400 ÷ 2 = 200, so x = 600 ÷ 2 = 300 b 600 ÷ 3 = 200, so x = 400 ÷ 3 = 133·3 c 600 ÷ 4 = 150, so x = 400 ÷ 4 = 100 The rate is 350 kM per 24 litres = 350/24 km per litre = 14·58 km/L. On 40 L the car will travel 40 × 14·6 km = 583 km. 1WORKEDExample 2WORKEDExample Jan and Dean built a bird-bath which they sold at the markets for \$140. They agreed that Jan had spent 4 hours building it and that Dean had worked for 3 hours. If the money is split in the same ratio as the time they spent, how much does each of them receive? Solution Jan : Dean 4 : 3 Total number of hours = 7 So Jan gets of \$140 = \$80 and Dean gets of \$140 = \$60 4 7 --- 3 7 --- 3WORKEDExample
12. 12. SkillSHEET answers Try these 1 If these ratios are all equivalent to 30 : 48, ﬁnd the missing number. a 120 : x b x : 240 c x : 36 2 If these ratios are all equivalent to 25 : 200, ﬁnd the missing number. a 200 : x b x : 2 c x : 150 3 If a car travels 250 km on 22 L of petrol, express this rate in kilometres per litre and calculate the amount of petrol needed by this car for a journey of 600 km. 4 If a car travels 150 km on 18 L of petrol, express this rate in kilometres per litre and calculate the amount of petrol needed by this car for a journey of 500 km. 5 A weed-killer concentrate should be mixed with water in the ratio of 25 mL to 2000 mL (2 L). If there is only 15 mL of the concentrate remaining, how much water should be mixed with it? 6 Patsy and Crystal set up a screen printing business, with Patsy contributing \$1200 and Crystal \$700. How should the ﬁrst month’s proﬁt of \$400 be distributed? 7 The Green Pines resort charges \$624 per person for a 7-night stay. At the same rate what would you expect to pay for a 2-night stay? 8 To stay 5 nights at the Cool Breeze Caravan Park costs \$47·50. What would you pay for 2 nights at the same rate? 9 A car travels at 80 km/h. Express this rate in these units. a metres/hour b metres/minute c metres/second d hours/100 kilometres 10 Hewey Lewis can run 100 m in 12 s. How fast is this in km/h? 11 The speed of sound is 340 m/s. a What is this speed in km/h? b In the 200-metre event the starting gun is 170 m from the timers. If we assume that the smoke from the gun is seen as soon as the gun is ﬁred, how much of a time lag is there between when the ﬁring is seen and heard by the timers? If a timer were to start his watch on the sound of the gun, would the athletes’ recorded time be faster (lower) or slower (higher)? c For investigation: The speed of sound given here is its speed in air at sea level. How does it change as you go higher?
13. 13. SkillSHEET answers SkillSHEET 4.1 Rounding decimal numbers to 2 decimal places To round a decimal number correct to 2 decimal places, follow these steps: 1. Consider the digit in the third decimal place (that is, the thousandth’s place). 2. If it is less than 5, simply omit this digit and all digits that follow. (That is, omit all digits beginning from the third decimal place.) 3. If it is 5 or greater than 5, add 1 to the preceding digit (that is, the one in the hundredth’s place) and omit all digits beginning from the third decimal place. Note that the sign ≈ is read as ‘is approximately equal to’. Try these Round each of the following numbers correct to 2 decimal places. 1 0.322 2 0.257 3 1.723 4 2.555 5 4.308 6 12.195 7 8.4678 8 25.033 78 9 18.333 333 10 0.166 666 6 Round each of the following numbers correct to 2 decimal places. a 0.239 b 4.5842 THINK WRITE a The digit in the third decimal place is 9, which is greater than 5. So add 1 to the preceding digit (that is, to 3) and omit 9. a 0.239 ≈ 0.24 b The digit in the third decimal place is 4. Since it is less than 5, simply omit all digits beginning from the third decimal place (that is, omit 4 and 2). b 4.5842 ≈ 4.58 WORKEDExample
14. 14. SkillSHEET answers SkillSHEET 4.2 Multiplying decimal numbers by powers of 10 To multiply a decimal number by powers of 10, move the decimal point to the right one space for each zero in the power of 10. For example, to multiply by 10, move the decimal point one place to the right, while to multiply by 1000 move it three places to the right. Note that if there are not enough digits after the decimal point, we can always add extra zeros. Try these Calculate each of the following. 1 2.56 × 10 2 7.6 × 10 3 0.98 × 10 4 3.49 × 100 5 2.6 × 100 6 70.1 × 100 7 0.2 × 100 8 5.321 × 1000 9 10.2 × 1000 10 0.758 × 1000 11 2.5 × 10 000 12 3.576 × 10 000 13 0.003 × 1000 14 0.000 6 × 10 000 15 0.000 08 × 100 000 16 0.04 × 10 000 Calculate each of the following. a 5.67 × 10 b 0.7 × 100 THINK WRITE a To multiply a decimal by 10, move the decimal point one place to the right (as there is one zero in 10). a 5.67 × 10 = 56.7 b To multiply a decimal by 100, we need to move the decimal point two places to the right. However, there is only one digit after the decimal (7). So add a zero ﬁrst (to create two decimal places), then move the decimal point two places to the right. Note that we write the answer as 70, rather than 070. b 0.7 × 100 = 0.70 × 100 = 70 WORKEDExample
15. 15. SkillSHEET answers SkillSHEET 4.3 Multiplying decimal numbers by 100 To multiply a decimal number by 100, move the decimal point two places to the right. Note that if there are not enough digits after the decimal point, we can always add extra zeros. Try these Calculate each of the following. 1 0.56 × 100 2 0.76 × 100 3 0.98 × 100 4 0.49 × 100 5 2.6 × 100 6 1.1 × 100 7 0.2 × 100 8 5.321 × 100 9 10.2 × 100 10 0.758 × 100 11 0.5 × 100 12 0.0006 × 100 Calculate each of the following. a 0.67 × 100 b 0.7 × 100 THINK WRITE a To multiply a decimal number by 100, move the decimal point two places to the right. Note that we do not write the zero in front of the number and the decimal point at the end of the number (that is, we write 67, rather than 067.). a 0.67 × 100 = 67 b We need to move the decimal point two places to the right; however, there is only one digit after the decimal point (7). So add a zero ﬁrst (to create two decimal places), then move the decimal point. b 0.7 × 100 = 0.70 × 100 = 70 WORKEDExample
16. 16. SkillSHEET answers SkillSHEET 4.4 Dividing whole numbers and decimals by 100 To divide a whole or a decimal number by 100, move the decimal point two places to the left. Note that although a whole number does not have a decimal point, we can always add it at the end of the number. (For example, 35 and 35. are the same numbers.) Also note that if there are not enough digits to move the decimal point the required number of places, we can always add extra zeros. Try these 1 Calculate each of the following. a 28 ÷ 100 b 60 ÷ 100 c 34 ÷ 100 d 2 ÷ 100 e 15 ÷ 100 f 7 ÷ 100 g 560 ÷ 100 h 721 ÷ 100 i 3 ÷ 100 j 75 ÷ 100 k 600 ÷ 100 l 250 ÷ 100 2 Calculate each of the following. a 9.2 ÷ 100 b 52.3 ÷ 100 c 0.5 ÷ 100 d 8.19 ÷ 100 e 4.9 ÷ 100 f 123.4 ÷ 100 g 0.3 ÷ 100 h 71.1 ÷ 100 i 155.6 ÷ 100 j 4.25 ÷ 100 k 75.3 ÷ 100 l 100.5 ÷ 100 Calculate each of the following. a 34 ÷ 100 b 350 ÷ 100 c 75.6 ÷ 100 d 4.1 ÷ 100 THINK WRITE a Put a decimal point at the end of the whole number. a 34 ÷ 100 = 34. ÷ 100 To divide by 100, move the decimal point 2 places to the left. Add a zero in front of the decimal point. 34 ÷ 100 = 0.34 b Put a decimal point at the end of the whole number. b 350 ÷ 100 = 350. ÷ 100 Move the decimal point 2 places to the left. You may wish to rewrite your answer, omitting the zero at the end of the resulting decimal (as 3.50 = 3.5). 350 ÷ 100 = 3.50 350 ÷ 100 = 3.5 c Move the decimal point 2 places to the left and add a zero in front of it. c 75.6 ÷ 100 = 0.756 d Move the decimal point two places to the left. (Add some extra zeros in front of the number as you go.) d 4.1 ÷ 100 = 0.041 1 2 1 2 WORKEDExample
17. 17. SkillSHEET answers SkillSHEET 4.5 Finding the size of a sector in degrees, given its size as a fraction of a circle There are 360° in a full circle. So to ﬁnd the size of a sector in degrees, given its size as a fraction of a full circle, multiply the fraction by 360°. To multiply a fraction by 360°: 1. change 360 into a fraction by writing it over 1 2. simplify as much as possible 3. multiply the numerators together and the denominators together 4. if the answer is an improper fraction, convert it to a mixed number. Try these Find the size of each of the following sectors in degrees, given that their size as a fraction of a circle is: 1 2 3 4 5 6 7 8 9 10 11 12 Finding the size of a sector in degrees, if the sector is of a circle. THINK WRITE To express a fraction of a circle in degrees, multiply by 360. × 360 Convert 360 into a fraction by writing it over 1. = × Cross-cancel 5 and 360 by dividing each by 5 (that is, 360 ÷ 5 = 72; 5 ÷ 5 = 1). = × Multiply the numerators together and the denominators together. = Convert the improper fraction into a mixed number (which in this case is actually a whole number) and include the degree sign. = 216° 3 5 --- 1 3 5 --- 2 3 5 --- 360 1 --------- 3 3 1 --- 72 1 ------ 4 216 1 --------- 5 WORKEDExample 2 5 --- 1 3 --- 3 10 ------ 3 4 --- 5 12 ------ 2 9 --- 7 8 --- 4 15 ------ 4 5 --- 1 6 --- 23 36 ------ 29 60 ------
18. 18. SkillSHEET answers SkillSHEET 6.1 Trigonometry review 1 A trigonometric function is a function of any angle (θ) inside a right angled triangle and can be deﬁned as the ratio of two sides of a right angled triangle. Sine (abbreviated as sin), cosine (abbreviated as cos) and tangent (abbreviated as tan) are used to deﬁne the ratios of the sides. Try these 1 For each of the following right angled triangles, identify the side labelled x in respect to the given angle θ. Where appropriate, also identify the side labelled y. a b c d e f g h i 2 For each of the triangles in question 1, identify which trigonometric function (sine, cosine or tangent) could be used to write an equation to ﬁnd x. sin θ = or cos θ = or tan θ = or opposite hypotenuse --------------------------- Hypotenuse Opposite side θ Hypotenuse Opposite side θ adjacent hypotenuse --------------------------- Hypotenuse Adjacent side θ Hypotenuse Adjacent side θ opposite adjacent -------------------- Opposite side Adjacent side θ Opposite side Adjacent side θ θ 10 cm x θ 10 cm x θ 10 cm x θ 10 cm 8 cm x θ 10 cm x θ 6 cm x θ 15 mm xy θ 6 cm x y θ 8 cmx y
19. 19. SkillSHEET answers SkillSHEET 6.2 Trigonometry review 2 The sine, cosine or tangent of an angle can be obtained simply from a scientiﬁc or graphics calculator. For example, to calculate sin 30°: 1. with a scientiﬁc calculator: Enter 30 then press . 2. with a graphics calculator: Press then enter 30 and press . Caution: Before entering the angle, check that the calculator is in DEGree mode. Try these 1 Find the value of the following, giving answers correct to 4 decimal places: a sin 15° b sin 34° c sin 79° d sin 20°46′ e sin 37°25′ f sin 83°17′ g cos 15° h cos 34° i cos 79° j cos 20°46′ k cos 37°25′ l cos 83°17′ m tan 15° n tan 34° o tan 79° p tan 20°46′ q tan 37°25′ r tan 83°17′ 2 Find the value of the following, giving answers correct to 3 decimal places: a sin 90° b cos 90° c tan 180° d sin 220°50′ e cos 139°25′ f tan 283°30′ g sin 115° h cos 234° i tan 370° j sin 180° k cos 180° l tan 90° SIN SIN ENTER Find: a sin 35∞ (to 4 decimal places) b sin 35∞30¢ (to 4 decimal places). Solution Solution a sin 35° = 0.5736 b 30′ means 30 minutes or 0.5° so sin 35°30′ is the same as sin 35.5°. sin 35°30′ = 0.5807 1WORKEDExample Find: a cos 45∞ (to 3 decimal places) b cos 45∞20¢ (to 3 decimal places). Solution Solution a cos 45° = 0.707 b cos 45°20′ = 0.703 (Note: cos 45°20′ is the same as cos 45.333°) 2WORKEDExample Find: a tan 60∞ (to 2 decimal places) b tan 60∞52¢ (to 2 decimal places). Solution Solution a tan 60° = 1.73 b tan 60°52′ = 1.79 (Note: tan 60°52′ is the same as tan 60.867°) 3WORKEDExample
20. 20. SkillSHEET answers To ﬁnd the angle when the sine, cosine or tangent value is given, use the inverse or 2nd function keys. Try these 3 Find the value of θ in each of the following. Where appropriate, give your answer in degrees and minutes. a sin θ° = 0.5 b sin θ° = 0.3145 c sin θ° = 0.7974 d sin θ° = 0.866 e cos θ° = 0.5 f cos θ° = 0.3145 g cos θ° = 0.7974 h cos θ° = 0.866 i tan θ° = 0.5 j tan θ° = 0.3145 k tan θ° = 0.7974 l tan θ° = 0.866 m tan θ° = 0.95 n tan θ° = 3.145 o tan θ° = 1.79 p tan θ° = 2.567 Find the value of angle θ, if sin θ∞ = 0.55, giving your answer in degrees and minutes. Solution θ° = sin-1 0.55 θ° = 33.3670° (degrees only) or 33°22' (degrees and minutes) 4WORKEDExample Find the value of angle θ, if cos θ∞ = 0.55, giving your answer in degrees and minutes. Solution θ° = cos−1 0.55 θ° = 56.63299° or 56°38′ 5WORKEDExample Find the value of angle θ, if tan θ∞ = 55, giving your answer in degrees and minutes. Solution θ° = tan−1 0.55 θ° = 28.8108° or 28°49′ 6WORKEDExample
21. 21. SkillSHEET answers SkillSHEET 7.1 Conversion of units — length Common units are: millimetre (mm), centimetre (cm), metre (m), kilometre (km) 10 mm = 1 cm 100 cm = 1 m 1000 m = 1 km ÷ 10 ÷ 100 ÷ 1000 mm cm m km × 10 × 100 × 1000 Remember: Converting to a smaller unit → Multiply Converting to a larger unit → Divide Try these Convert each of the following measurements to the unit shown in the brackets. 1 2 m (cm) 2 53 mm (cm) 3 610 km (m) 4 0.0003 km (cm) 5 5600 mm (m) 6 11.3 cm (mm) 7 12 304 m (km) 8 0.0007 m (mm) 9 6300 mm (m) 10 0.8 km (m) 11 0.011 km (cm) 12 0.0042 km (mm) 13 9000 mm (m) 14 765 m (km) 15 0.000 089 km (mm) 16 14 683 mm (km) Convert 5 centimetres to millimetres. Convert 80 000 centimetres to kilometres. Solution Solution Converting to a smaller unit so we need to multiply. To convert cm to mm, multiply by 10. 5 cm × 10 = 50 mm Converting to a larger unit so we need to divide. To convert cm to km, divide ﬁrst by 100 (to convert to m) then by 1000 (to convert to km). 80 000 cm ÷ 100 = 800 m 800 m ÷ 1000 = 0.8 km 1WORKEDExample 2WORKEDExample
22. 22. SkillSHEET answers SkillSHEET 7.2 Reading scales (How much is each interval worth?) When reading scales it is important to remember that the intervals between the adjacent marks are equal. To ﬁnd the value of each interval, ﬁnd the value of the section of the scale whose end points are known (that is, the length between the adjacent major marks) and then divide by the number of intervals along this section. Try these For each of the following scales, ﬁnd how much each interval is worth. 1 2 3 4 5 6 7 8 9 10 For each of the following scales, ﬁnd how much each interval is worth. a b c THINK WRITE a Find the value of the section of the scale between the major marks by calculating the difference between the end points. a 30 − 20 = 10 There are 10 intervals between the major marks. So, to ﬁnd the value of each interval, divide the value of the section of the scale by 10. 10 ÷ 10 = 1 Write the answer in words. Each interval is worth one unit. b Repeat steps 1–3 as in part a. b 6 − 5 = 1 1 ÷ 10 = 0.1 Each interval is worth 0.1 of a unit. c Repeat steps 1–3 as in part a. c 200 − 100 = 100 100 ÷ 5 = 20 Each interval is worth 20 units. 20 30 5 6 100 200 1 2 3 WORKEDExample 40 50 70 80 11 12 23 24 10 20 300 400 8 9 20 30 400 500 4000 5000
23. 23. SkillSHEET answers SkillSHEET 7.3 Pythagoras’ theorem In any right-angled triangle the square of the hypotenuse is equal to the sum of the squares of the other two sides. This known as Pythagoras’ theorem. For the triangle shown, Pythagoras’ theorem can be written as c2 = a2 + b2 . b c a Find the length of x to 1 decimal place. Find the length of y to 1 decimal place. Solution Solution The hypotenuse is x (which relates to c in the formula) and the other side lengths are 5 and 6 (which relate to a and b in the formula). c2 = a2 + b2 x2 = 52 + 62 = 25 + 36 = 61 x = (Take the square root of both sides) =7.8 The hypotenuse is 15 (which relates to c in the formula) and the other side lengths are y and 11 (which relate to a and b in the formula). c2 = a2 + b2 152 = y2 + 112 225 = y2 + 121 y2 + 121 = 225 (Swap sides to bring the y term to the left side) y2 = 225 − 121 (Subtract 121 from both sides) = 104 y = (Take the square root of both sides) = 10.2 6 5 x 1115 y 61 104 1WORKEDExample 2WORKEDExample
24. 24. SkillSHEET answers Try these For each of the following triangles, ﬁnd the value of the pronumeral correct to 1 decimal place. 1 2 3 4 5 6 7 8 11 x 7 19 y 28 10 13 a 25 14 x 17 3 k 135 73 m 19.8 8.5 x 0.6 0.7 x
25. 25. SkillSHEET answers SkillSHEET 7.4 Using trigonometric ratios Trigonometric ratios deal with right-angled triangles. The sides of the triangle are named according to their pos- ition with respect to a speciﬁc angle. The hypotenuse is the longest side length of the right-angled triangle. Trigonometric ratios: SOH CAH TOA means sin θ = , cos θ = and tan θ = Hypotenuse Opposite side with respect to the angle θ θ Adjacent side with respect to the angle θ opposite hypotenuse ---------------------------- adjacent hypotenuse ---------------------------- opposite adjacent -------------------- Find the value of x. Express your answer Find the value correct to 3 decimal places. of x. Express your answer correct to 2 decimal places. Solution Solution Given information is: Angle is 47°, hypotenuse length is 18 cm. The side marked x is the opposite side. Use the sine ratio: sin θ = sin 47° = = sin 47° x = 18 × sin 47° x = 13.164 cm Given information is: Angle = 30°, hence the adjacent side = 45 mm. The side marked x is the hypotenuse. Use the cosine ratio: cos θ = cos 30° = x cos 30° = 45 x = x = 51.96 mm 45 mm 30° x 18 cm x 47° opposite hypotenuse --------------------------- x 18 ------ x 18 ------ adjacent hypotenuse --------------------------- 45 x ------ 45 cos 30° ----------------- 1WORKEDExample 2WORKEDExample
26. 26. SkillSHEET answers Try these 1 For the following right-angled triangles state which trigonometric ratio would be appropriate in ﬁnding the side length marked x. a b c d e 2 Find the side length marked x for each of the triangles in question 1. Express your answers correct to 3 decimal places. Find the value of the angle θ, to the nearest degree. Solution Given information is: Opposite side is 24 mm and adjacent side is 37 mm. Use tangent ratio: tan θ = tan θ = tan θ = 33° 24 mm 37 mm θ opposite adjacent -------------------- 24 37 ------ 3WORKEDExample 6 cmx 45° 7 cmx 15° 4 cm x 20° 13 cm x 73° 10 cm x 27°
27. 27. SkillSHEET answers 3 Find the value of the angle in each of the following triangles. Express your answer to the nearest degree. a b c d e 22 cm 15 cm θ 31 mm 39 mm θ 10 cm 12 cm θ 8.3 cm 5.9 cm θ 0.52 m 1.34 m θ
28. 28. SkillSHEET answers SkillSHEET 7.5 Identifying sides of a right-angled triangle with respect to the given angle. In a right-angled triangle, the longest side (which is opposite the right angle) is called the hypotenuse. The other two sides are named depending on their position with respect to the given angle. The side opposite to the given angle is called the opposite side and the side next to the given angle is called the adjacent side. Observe the two triangles below. In the triangle at left, side a is opposite and side b is adjacent, while in the triangle at right side a is adjacent and side b is opposite. This is because sides are named according to their position in relation to a given angle and in the two triangles above the given angle is not the same. Try these For each of the following right-angled triangles identify the side labelled x with respect to the given angle θ. Where necessary, identify also the side labelled y. 1 2 3 4 5 6 7 8 9 Side a Side b θ Opposite side Hypotenuse Adjacent side Side a Side b θ Adjacent side Hypotenuse Opposite side For each of the following right-angled triangles, identify the side labelled x with respect to the given angle θ. Where necessary, also identify the side labelled y. a b Solution Solution a The side labelled x is directly opposite angle θ. So x is the opposite side. b The side labelled x is next to given angle θ, and the side labelled y is opposite the right angle. So x is the adjacent side and y is the hypotenuse. x θ 12 cm x y θ WORKEDExample x 10 cm θ x 10 cm θ x 10 cm θ x 10 cm θ 8 cm x 10 cm θ x 6 θ x y θ 15 mm xy θ 6 cm x y θ 8 mm
30. 30. SkillSHEET answers Try these 1 Find the value of each of the following, giving answers correct to 4 decimal places. a sin 15° b sin 34° c sin 79° d sin 20° e sin 37° f sin 83° g cos 15° h cos 34° i cos 79° j cos 20° k cos 37° l cos 83° m tan 15° n tan 34° o tan 79° p tan 20° q tan 37° r tan 83° 2 For each of the following, ﬁnd the value of θ, giving answers correct to 1 decimal place. a sin θ° = 0.5 b sin θ° = 0.3145 c sin θ° = 0.7974 d sin θ° = 0.866 e cos θ° = 0.5 f cos θ° = 0.3145 g cos θ° = 0.7974 h cos θ° = 0.866 i tan θ° = 0.5 j tan θ° = 0.3145 k tan θ° = 0.7974 l tan θ° = 0.866 m tan θ° = 0.95 n tan θ° = 3.145 o tan θ° = 1.79 p tan θ° = 2.567 Solution b To ﬁnd the value of an angle when given the value of its cosine, press , enter 0.5505 and press . Record the number shown on the display and round it off to 1 decimal place. cos θ° = 0.5505 cos° θ = cos−1 0.5505 cos° θ = 56.598 678 18 cos° θ ≈ 56.6° c To ﬁnd the value of an angle when given the value of its tangent, press , enter 0.5505 and press . Record the number shown on the display and round it off to 1 decimal place. tan θ° = 0.5505 tan° θ = tan−1 0.5505 tan° θ = 28.832 783 64 tan° θ ≈ 28.8° 2nd [COS-1 ] = 2nd [TAN-1 ] =
31. 31. SkillSHEET answers SkillSHEET 8.1 Area and perimeter of composite ﬁgures Composite ﬁgures are ﬁgures made up of a number of distinct shapes. Area of a composite ﬁgure = sum of the areas of each individual shape Perimeter of a composite ﬁgure = length around the outside edge of the composite ﬁgure Calculate a the area and b the perimeter of Calculate a the area and b the perimeter of the the following shape. following shape. State your answers correct to 2 decimal places. Solution Solution The composite shape is made up of a rectangle and a triangle. a Area = area of rectangle + area of triangle Area = length × width + × base × height For the rectangle: Length = 16 cm, width = 12 cm For the triangle: Base = 12 cm (same as width of rectangle), Height = (24 − 16) = 8 cm So area = 16 × 12 + × 12 × 8 So area = 192 + 48 So area = 240 cm2 b Perimeter = sum of the lengths of 5 sides Perimeter = 16 + 10 + 10 + 16 + 12 Perimeter = 64 cm The composite shape is made up of a semicircle and a trapezium. a Area = area of semicircle + area of trapezium Area = πr2 + (a + b)h For the semi circle: r = × 30 = 15 mm For the trapezium: a = 30 mm, b = 48 mm and h = 15 mm. So area = × π × 152 + × (30 + 48) × 15 So area = 353.43 + 585 So area = 938.43 mm2 b Perimeter = (circumference of circle) + Perimeter = 3 side lengths of trapezium To ﬁnd missing side length of trapezium: Let c = hypotenuse of right-angled triangle with side lengths of 15 and 18 c2 = 152 + 182 (Using Pythagoras’ theorem) = 225 + 324 = 549 c = c = 23.43 So perimeter = × 2πr + 15 + 48 + 23.43 So perimeter = π × 15 + 86.43 So perimeter = 47.12 + 86.43 So perimeter = 133.55 mm 12 cm 16 cm 24 cm 10 cm 15 m 48 m 30 m 1 2 --- 1 2 --- 1 2 --- 1 2 --- 1 2 --- 1 2 --- 1 2 --- 1 2 --- 549 1 2 --- 1WORKEDExample 2WORKEDExample
32. 32. SkillSHEET answers Try these Calculate a the area and b the perimeter of each of the following shapes. State your answers correct to 2 decimal places where appropriate. 1 2 3 4 5 6 10 m 18 m 30 m 13 m 20 cm 10 cm 6 cm 18 cm 49 cm 23 cm 35 cm 12 m 9 m 7 m 3 mm 3 mm 3 mm 3 mm 5 mm 15 mm 5 cm 7 cm
33. 33. SkillSHEET answers SkillSHEET 8.2 Volume The volume of an object is the amount of space that the object occupies. Some examples of volume units are: mm3 , cm3 and m3 . Prisms: V = cross-sectional area × height of prism Tapered objects: V = × area of base × height of object Sphere: V = πr3 Try these Find the volume of each of the following shapes. State your answers correct to 2 decimal places (where appropriate). 1 2 3 4 5 6 1 3 --- 4 3 --- Find the volume of the following shape. Find the volume of the following shape. Express your answer correct to 2 decimal places. Solution Solution The shape is a rectangular prism. V = cross-sectional area × height V = area of rectangle × height V = 12 × 5 × 7 V = 420 cm3 The shape is a cone (tapered object). V = × area of base × height of object V = × area of circle × height of object V = × πr2 × H V = × π × 32 × 10 V = 94.25 m3 7 cm 5 cm 12 cm 6 m 10 m 1 3 --- 1 3 --- 1 3 --- 1 3 --- 1WORKEDExample 2WORKEDExample 19 m 8 m 26 m 4 cm 9 cm 8 mm 6 mm 16 mm 2 cm 8 cm 13 cm 9 cm 5 cm 27.2 m 11.5 m
34. 34. SkillSHEET answers 7 8 9 10 11 12 16 cm 21 cm 14 cm 17 m38 m 5.7 cm 12.4 cm 6 mm 15 mm 7 mm 4 mm 42 cm 65 cm
35. 35. SkillSHEET answers SkillSHEET 8.3 Conversion of units — volume Common units for volume are: cubic millimetre (mm3 ), cubic centimetre (cm3 ) and cubic metre (m3 ). 10 mm = 1 cm → 103 mm3 = 13 cm3 so 1000 mm3 = 1 cm3 100 cm = 1 m → 1003 cm3 = 13 m3 so 1 000 000 cm3 = 1 m3 ÷ 103 ÷ 1003 mm3 cm3 m3 × 103 ×1003 Remember: converting to a smaller unit → multiply converting to a larger unit → divide Try these Convert each of the following measurements to the unit shown in brackets. 1 268 mm3 (cm3 ) 2 0.035 m3 (cm3 ) 3 0.000 610 cm3 (mm3 ) 4 37.569 cm3 (m3 ) 5 5.03 cm3 (mm3 ) 6 68 005 624 cm3 (m3 ) 7 3.1 m3 (mm3 ) 8 15 000 000 000 mm3 (m3 ) 9 86 mm3 (m3 ) 10 0.0704 m3 (mm3 ) Convert 2300 mm3 to cm3 . Convert 3.057 m3 to cm3 . Solution Solution Converting to a larger unit so we need to divide. To convert mm3 to cm3 , divide by 1000. 2300 mm3 ÷ 1000 = 2.3 cm3 Converting to a smaller unit so we need to multiply. To convert m3 to cm3 , multiply by 1 000 000. 3.057 m3 × 1 000 000 = 3 057 000 cm3 1WORKEDExample 2WORKEDExample
36. 36. SkillSHEET answers SkillSHEET 8.4 Labelling right-angled triangles In trigonometry, the sides of right-angled triangles are named according to their position relative to a speciﬁc angle (not the right angle). The symbol θ (theta) is one of many Greek letters of the alphabet used to represent this speciﬁc angle. If the speciﬁc angle is θ, then the side of the triangle opposite θ is called the opposite side the longest side of the triangle, opposite the right angle, is called the hypotenuse the third side, next to the angle θ, is called the adjacent side Try these 1 Label the sides of each of the following triangles using the words Opposite, Adjacent, and Hypotenuse. a b c d e f g h Hypotenuse Opposite side with respect to the angle θ θ Adjacent side with respect to the angle θ 45° x 6 cm 22 cm 15 cm θ 18 cm x 47° 10 cm 12 cm θ 73° x 13 cm 27° 10 cm x 8.3 cm 5.9 cm θ 24 mm 37 mm θ
37. 37. SkillSHEET answers i j 2 For each triangle in question 1, list the two sides which provide information. That is, which two of Opposite, Adjacent and Hypotenuse have either a known value or a pronumeral. x 7 cm 15° 20° x 4 cm
38. 38. SkillSHEET answers SkillSHEET 8.5 Using trigonometric ratios Trigonometric ratios deal with right-angled triangles. The sides of the triangle are named according to their pos- ition with respect to a speciﬁc angle. The hypotenuse is the longest side length of the right-angled triangle. Trigonometric ratios: SOH CAH TOA means sin θ = , cos θ = and tan θ = Hypotenuse Opposite side with respect to the angle θ θ Adjacent side with respect to the angle θ opposite hypotenuse ---------------------------- adjacent hypotenuse ---------------------------- opposite adjacent -------------------- Find the value of x. Express your answer Find the value correct to 3 decimal places. of x. Express your answer correct to 2 decimal places. Solution Solution Given information is: Angle is 47°, hypotenuse length is 18 cm. The side marked x is the opposite side. Use the sine ratio: sin θ = sin 47° = = sin 47° x = 18 × sin 47° x = 13.164 cm Given information is: Angle = 30°, hence the adjacent side = 45 mm. The side marked x is the hypotenuse. Use the cosine ratio: cos θ = cos 30° = x cos 30° = 45 x = x = 51.96 mm 30° x 45 mm18 cm x 47° opposite hypotenuse --------------------------- x 18 ------ x 18 ------ adjacent hypotenuse --------------------------- 45 x ------ 45 cos 30° ----------------- 1WORKEDExample 2WORKEDExample
39. 39. SkillSHEET answers Try these 1 For the following right-angled triangles state which trigonometric ratio would be appropriate in ﬁnding the side length marked x. a b c d e 2 Find the side length marked x for each of the triangles in question 1. Express your answers correct to 3 decimal places. Find the value of the angle θ, to the nearest degree. Solution Given information is: Opposite side is 24 mm and adjacent side is 37 mm. Use tangent ratio: tan θ = tan θ = tan θ = 33° 24 mm 37 mm θ opposite adjacent -------------------- 24 37 ------ 3WORKEDExample 45° 6 cm x 15° 7 cmx 20° 4 cm x 73° 13 m x 27° 10 cm x
40. 40. SkillSHEET answers 3 Find the value of the angle in each of the following triangles. Express your answer to the nearest degree. a b c d e 22 cm 15 cm θ 31 mm 39 mm θ 10 cm 12 cm θ 8.3 cm 5.9 cm θ 0.52 m 1.34 m θ
41. 41. SkillSHEET answers SkillSHEET 9.1 Finding the size of a sector in degrees, given its size as a fraction of a circle There are 360° in a full circle. So to ﬁnd the size of a sector in degrees, given its size as a fraction of a full circle, multiply the fraction by 360°. To multiply a fraction by 360°: 1. change 360 into a fraction by writing it over 1 2. simplify as much as possible 3. multiply the numerators together and the denominators together 4. if the answer is an improper fraction, convert it to a mixed number. Try these Find the size of each of the following sectors in degrees, given that their size as a fraction of a circle is: 1 2 3 4 5 6 7 8 9 10 11 12 Finding the size of a sector in degrees, if the sector is of a circle. THINK WRITE To express a fraction of a circle in degrees, multiply by 360. × 360 Convert 360 into a fraction by writing it over 1. = × Cross-cancel 5 and 360 by dividing each by 5 (that is, 360 ÷ 5 = 72; 5 ÷ 5 = 1). = × Multiply the numerators together and the denominators together. = Convert the improper fraction into a mixed number (which in this case is actually a whole number) and include the degree sign. = 216° 3 5 --- 1 3 5 --- 2 3 5 --- 360 1 --------- 3 3 1 --- 72 1 ------ 4 216 1 --------- 5 WORKEDExample 2 5 --- 1 3 --- 3 10 ------ 3 4 --- 5 12 ------ 2 9 --- 7 8 --- 4 15 ------ 4 5 --- 1 6 --- 23 36 ------ 29 60 ------
42. 42. SkillSHEET answers SkillSHEET 10.1 Finding a mean To ﬁnd the mean of two or more numbers, add the numbers together and then divide the sum by the number of numbers. Try these Find the mean of each of the following sets of numbers. 1 3, 5 2 2, 9 3 2, 4, 8 4 5, 6, 9 5 4, 7, 8, 12 6 7, x 7 x, 19 8 x, 5, 12 9 2, 4, x 10 17, x, 25 Find the mean of each of the following sets of numbers. a 2, 3, 7 b 5, x THINK WRITE a To ﬁnd the mean of three numbers, add them together and then divide by 3. a Average = Evaluate the numerator of the fraction ﬁrst and then divide. Average = Average = 4 b To ﬁnd the mean of two numbers, add them together and divide the total by 2. (Since the value of x is not given, the expression can not be evaluated and should be left as is.) b Average = 1 2 3 7+ + 3 --------------------- 2 12 3 ------ 5 x+ 2 ------------ WORKEDExample
43. 43. SkillSHEET answers SkillSHEET 10.2 Finding the median The median of a set of scores is the middle score when the data are arranged in order of size. The position of the median is found using the formula: Median position = score where n is the number of scores. For example, if there are 13 scores, the median position is the score; that is, the 7th score. If there are 16 scores, the median position is the score; that is, the 8 th score. The 8 th score is halfway between and is equal to the average of the 8th and 9th scores. Try these Find the median of each of the following sets of data. 1 7, 5, 8, 9, 2, 4, 5, 1, 8, 2, 5 2 21, 19, 28, 25, 17, 24, 22, 25, 19 3 32, 45, 58, 21, 57, 84, 26 4 52, 59, 48, 53, 49, 56, 58, 42, 60 5 12, 5, 7, 9, 5, 14, 7, 2, 9, 5, 4, 1 6 27, 40, 33, 37, 46, 32, 19, 21 7 9, 7, 8, 12, 6, 13, 14, 11, 5, 10 8 20, 16, 26, 21, 15, 20 n 1+( )th 2 ---------------------- 13 1+( )th 2 ------------------------- 16 1+( )th 2 ------------------------- 1 2 --- 1 2 --- Find the median of the following set of data: 8, 3, 7, 4, 9, 1, 5, 8, 6, 13, 12, 2, 6. Find the median of the following set of data: 28, 33, 27, 29, 29, 29, 32, 28, 34, 31, 32, 33. Solution Solution There are 13 scores. ∴ n = 13 Median score = = = the 7th score. Arrange the data in order of size and locate the seventh score. 1, 2, 3, 4, 5, 6, , 7, 8, 8, 9, 12, 13. So, median = 6. There are 12 scores. ∴ n = 12 Median score = = = the 6 th score. Rewrite the data in order of size. The median is located halfway between the 6th and 7th scores. 27, 28, 28, 29, 29, , 32, 32, 33, 33, 34. To ﬁnd the median, calculate the average of the 6th and 7th scores. Median = = = 30 n 1+( )th 2 ---------------------- 13 1+( )th 2 ------------------------- 6 n 1+( )th 2 ---------------------- 12 1+( )th 2 ------------------------- 1 2 --- 29, 31 29 31+ 2 ------------------ 60 2 ------ 1WORKEDExample 2WORKEDExample
44. 44. SkillSHEET answers SkillSHEET 11.1 Measuring the rise and the run To measure the rise and the run for a straight line, follow these steps: 1. Select two points on the line. If the line goes through the origin, it is best to select the origin and any other point. If the line cuts both axes, select the x-intercept and the y-intercept. 2. Construct the gradient triangle, so that the two points are the vertices. 3. Measure the horizontal distance (that is, the distance along the horizontal side of a triangle) between the two points. This distance represents the run. Note that the run is always positive. 4. Measure the vertical distance (that is, the distance along the vertical side of a triangle) between the two points. This distance represents the rise. Note that if the line slopes upward from left to right, the rise is positive, while if the line slopes downward, the rise is negative. State the rise and the run for each of the following straight lines. a b THINK WRITE/DRAW a Since the line goes through the origin, select the origin and some other point. Draw the gradient triangle so that the selected points are the vertices. a Measure the distance along the horizontal side of the triangle (that is, how much it is from 0 to 2). Hence state the value of the run. Run = 2 Measure the distance along the vertical side of the triangle (that is, how much it is from 0 to 3) to ﬁnd the value of the rise. Since the line slopes upward from left to right, the rise is positive. Rise = 3 y x 4 3 2 1 –1 –2 –3 –4 –1 1 2 3 4–2–3–4 y x 4 2 1 3 –2 –3 –1 –4 2 31 4 5 6–2–3 –1 1 y 4 3 2 1 –1 –2 –3 –4 –1 1 2 3 4–2–3–4 2 3 2 3 WORKEDExample
45. 45. SkillSHEET answers Try these State the rise and the run for each of the following straight lines. 1 2 3 4 5 6 THINK WRITE/DRAW b Since the line cuts both axes, select the x- and y-intercepts. Draw the gradient triangle so that the selected points are the vertices. b Measure the distance along the horizontal side of the triangle (it is from 0 to 6) and hence state the value of the run. Run = 6 Measure the distance along the vertical side of the triangle (that is, from 0 to 2) to ﬁnd the value of the rise. Since the line slopes downward from left to right, the rise is negative. Rise = −2 1 y x 4 2 –2 6 1 3 –2 –3 –1 –4 2 31 4 5 6–2–3 –1 2 3 y x 4 2 1 3 –2 –3 –1 2 31 4 5 6–2–3 –1 y x 4 2 1 3 –2 –3 –1 2 31 4 5 6–2–3 –1 y x 4 5 2 1 3 –2 –3 –1 2 31 4 5 6–2–3 –1 y x 4 2 1 3 –2 –3 –1 2 31 4 5 6–2–3 –1 y x 4 2 1 3 –2 –3 –1 2 31 4 5 6–2–3 –1 y x 4 2 1 3 –2 –3 –1 2 31 4 5 6–2–3 –1
46. 46. SkillSHEET answers 7 8 9 10 y x 4 2 1 3 –2 –3 –1 2 31 4 5 6–2–3 –1 y x 4 2 1 3 –2 –3 –1 2 31 4 5 6–2–3 –1 y x 4 2 1 3 –2 –3 –1 2 31–2–3 –1 y x 2 1 3 –2 –4 –3 –1 21–2–4 –3 –1
47. 47. SkillSHEET answers SkillSHEET 11.2 Substitution into a rule To substitute a given value of the pronumeral into an algebraic sentence or rule means to replace the pronumeral with that value. When all pronumerals have been replaced with numbers, the expression can be evaluated. Order of operations must be observed at all times when evaluating. Try these 1 Substitute 5 for x in each of the following rules and then ﬁnd the value of y. a y = x + 9 b y = x − 3 c y = 12 + x d y = 25 − x e y = 4x f y = 7x g y = 3x − 4 h y = 2x + 6 i y = 25 − 3x j y = 11 + 6x 2 Substitute 3 for x in each of the rules in question 1 and hence ﬁnd the value of y. Substitute 5 for x in each of the following rules and then ﬁnd the value of y. a y = x + 7 b y = 2x − 3 THINK WRITE a Replace x with the given value (i.e. 5). The rest of the expression remains unchanged. a y = 5 + 7 Add 5 and 7 to ﬁnd the value of y. y = 12 b Substitute 5 for x, remembering that in algebra 2x means 2 × x. b y = 2 × 5 − 3 To ﬁnd the value of y, perform multiplication ﬁrst, followed by subtraction. y = 10 − 3 y = 7 1 2 1 2 WORKEDExample
48. 48. SkillSHEET answers SkillSHEET 11.3 Average rate of change If a rate is variable, it is sometimes useful to know the average rate of change over a speciﬁc interval from x1 to x2. Average rate of change = = = Try these 1 a For the function f(t) = 5t − 4t2 − 6, ﬁnd f(5) and f(7). b For the function h(t) = 8t − t2 − 3, ﬁnd h(1) and h(4). c For the function y = 7x − 4x2 − 1, ﬁnd the values of y when x = 2 and x = 4. 2 a Consider the function f(t) = 5t − 4t2 − 6 which deﬁnes the position of a particle at time t (seconds) from a ﬁxed point. Find the average rate of change (velocity) between t = 5 s to t = 7 s. b A discus is tossed so that its height, h metres above the ground, is given by the rule h(t) = 8t − t2 − 3, where t represents time in seconds. Find the average rate of change between t = 1 s to t = 4 s. c If y = 7x − 4x2 − 1, ﬁnd the average rate of change of y as x changes from 2 to 4. 3 The position of a ball, x cm from the start at time t s is given by x(t) = t + 6t3 . Find the average rate of change of position with respect to time (velocity) between t = 0 to t = 3. 4 The volume, V m3 , of dripping tap water into a bucket is increasing according to the rule V(t) = , time t (minutes) from the beginning. Find the average rate of change of volume of water between t = 2 to t = 5 minutes. 5 If y = x 3 − 4x2 − 1, ﬁnd the average rate of change of y as x changes from −3 to −1. rise run -------- change in f x( ) change in x ------------------------------------ f x2( ) f x1( )– x2 x1– --------------------------------- For f(x) = x2 - 4x + 1, ﬁnd the average rate of A cricket ball was hit so that its height (h) metres change between x = 1 and x = 2. above the ground followed the rule: h(t) = 5t - t2 , where t represents the time in seconds. Find the average rate of change over the ﬁrst 3 seconds. Solution Solution Average rate of change = where x1 = 1 and x2 = 2 = Now f(2) = (2)2 − 4(2) + 1 = 4 − 8 + 1 = −3 and f(1) = (1)2 − 4(1) + 1 = 1 − 4 + 1 = −2 So average rate of change = So average rate of change = So average rate of change = −1 Average rate of change = = = = 2 Average rate of change is 2 m/s. f x2( ) f x1( )– x2 x1– --------------------------------- f 2( ) f 1( )– 2 1– ----------------------------- −3 −2– 2 1– ------------------- 1– 1 ------ f 3( ) f 0( )– 3 0– ----------------------------- 5 3 3 2 –×( ) 5 0 0 2 –×( )– 3 0– --------------------------------------------------------------- 6 0– 3 ------------ 1WORKEDExample 2WORKEDExample t 1–( ) 3 1+ 2 ---------------------------
49. 49. SkillSHEET answers SkillSHEET 11.4 Using the regression equation to make predictions The regression equation can be used to predict a value of the dependent variable (y) given a value of the indepen- dent variable (x) and vice versa. Try these 1 For the regression equation y = 2x + 11 ﬁnd: a y if x = 5 b y if x = 23 c x if y = 93 d x if y = 214 2 For the regression equation y = 11x − 2 ﬁnd: a y if x = 4 b y if x = 60 c x if y = 75 d x if y = 125 3 For the regression equation y = 1.2x + 35.5 ﬁnd: a y if x = 20 b y if x = 56 c x if y = 120 d x if y = 65 4 For the regression equation y = 1.05x − 56 ﬁnd: a y if x = 65 b y if x = 80 c x if y = 45 d x if y = 38 5 For the regression equation y = 2.35x + 45 ﬁnd: a y if x = 30 b y if x = 65 c x if y = 80 d x if y = 480. For the regression equation y = 3x + 9 ﬁnd: a y if x = 7 b x if y = 72. Solution a Substitute 7 for x into the given equation and evaluate. y = 3x + 9, x = 7 y = 3 × 7 + 9 y = 21 + 9 (Perform multiplication ﬁrst, followed by addition.) y = 30 b Substitute 72 for y into the equation and solve for x. y = 3x + 9, y = 72 72 = 3x + 9 72 − 9 = 3x (Subtract 9 from both sides.) 63 = 3x 63 ÷ 3 = x (Divide both sides by 3.) x = 21 WORKEDExample
50. 50. SkillSHEET answers SkillSHEET 12.1 Understanding a deck of playing cards A standard deck of playing cards consists of 52 cards. All cards are divided into 4 suits. There are two black suits — spades (m) and clubs (p) and two red suits — hearts (n) and diamonds (o). In each suit there are 13 cards including a 2, 3, 4, 5, 6, 7, 8, 9, 10, a jack, a queen, a king and an ace. (Note that there is no 1.) A jack, a queen and a king are called picture cards. Try these For a standard deck of playing cards, state the number of: 1 black cards 2 aces 3 picture cards 4 queens of hearts 5 kings 6 clubs 7 not spades 8 red cards 9 tens 10 red jacks 11 black threes 12 red nines 13 number cards greater than 6 14 red picture cards. For a standard deck of playing cards, state the number of: a diamonds b black queens. THINK WRITE a Diamonds is one of the four suits and there are 13 cards in any suit. a There are 13 diamonds. b There is one queen in each suit and there are two black suits (clubs and spades). b There are 2 black queens. WORKEDExample
51. 51. SkillSHEET answers SkillSHEET 12.2 Converting fractions to percentages To convert a fraction into a percentage, multiply the fraction by 100%. Try these Convert each of the following fractions into percentages. 1 2 3 4 5 6 7 8 9 10 Convert each of the following fractions into percentages. a b THINK WRITE a To change the fraction to a percentage, multiply by 100%. a × 100% Write 100 as a fraction by putting it over 1. = × Multiply numerators together and denominators together. = Simplify by dividing 300 by 5. = 60% b To change the fraction to a percentage, multiply by 100%. b × 100% Write 100 as a fraction by putting it over 1. = × Multiply numerators together and denominators together. = Convert the improper fraction into a mixed number. = 66 % 3 5 --- 2 3 --- 1 3 5 --- 2 3 5 --- 100 1 --------- 3 300 5 --------- 4 1 2 3 --- 2 2 3 --- 100 1 --------- 3 200 3 --------- 4 2 3 --- WORKEDExample 3 4 --- 4 5 --- 3 8 --- 2 5 --- 7 8 --- 1 3 --- 5 6 --- 3 7 --- 5 9 --- 7 12 ------
52. 52. SkillSHEET answers SkillSHEET 12.3 Converting a fraction to a decimal number To convert any fraction into a decimal number, divide its numerator by the denominator. This can be easily done using a calculator. Try these Convert each of the following fractions into decimals. 1 2 3 4 5 6 7 8 9 10 Convert into a decimal. THINK WRITE To convert the given fraction into a decimal, divide 15 by 80. This can be done with the help of a scientiﬁc calculator by pressing the following sequence of buttons and recording the result: With a graphics calculator, press the keys for then ﬁnish by pressing . = 0.1875 15 80 ------ 15 ÷ 80 = 15 ÷ 80 ENTER 15 80 ------ WORKEDExample 15 40 ------ 5 16 ------ 7 8 --- 25 80 ------ 41 100 --------- 45 300 --------- 91 128 --------- 15 64 ------ 138 200 --------- 159 160 ---------