year 8 maths

222 Chapter 4 Fractions, decimals, percentages and financial mathematics
16 Joliet is a keen walker. She has a pedometer that shows she has walked 1 428 350 paces so far this
year. Her average pace length is 0.84 metres. How many kilometres has Joliet walked so far this
year? (Give your answer correct to the nearest kilometre.)
17 A steel pipe of length 7.234 m must be divided into four equal lengths. The saw blade is 2 mm
thick. How long will each of the four lengths be?
18 If a = 0.12, b = 2.3 and c = 3.42 , find:
a a + b + c b c − (a + b) c a × b × c d c ÷ a − b
19 If a = 0.1, b = 2.1 and c = 3.1 , without evaluating, which of the following alternatives would
provide the biggest answer?
A a + b + c B a × b × c C b ÷ a + c D c ÷ a × b
ENRICHMENT
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20
Target practice
20 In each of the following problems, you must come up with a starting decimal number(s) that will
provide an answer within the target range provided when the nominated operation is performed.
For example: Find a decimal number that when multiplied by 53.24 will give an answer between
2.05 and 2.1 .
You might like to use trial and error, or you might like to work out the question backwards.
Confirm these results on your calculator:
0.03 × 53.24 = 1.5972 (answer outside target range—too small)
0.04 × 53.24 = 2.1296 (answer outside target range—too large)
0.039 × 53.24 = 2.07636 (answer within target range of 2.05 to 2.1 )
Therefore, a possible answer is 0.039 .
Try the following target problems. (Aim to use as few decimal places as possible.)
Question Starting number Operation (instruction) Target range
1 0.039 × 53.24 2.05–2.1
2 × 0.034 100–101
3 ÷ 1.2374 75.7–75.8
4 × by itself (square) 0.32–0.33
5 ÷ (−5.004) 9.9–9.99
Try the following target problems. (Each starting number must have at least two decimal places.)
Question Two starting numbers Operation (instruction) Target range
6 0.05, 3.12 × 0.1–0.2
7 ÷ 4.1–4.2
8 × 99.95–100.05
9 + 0.001–0.002
10 – 45.27
You might like to make up some of your own target problems.
Cambridge Maths NSW
Stage 4 Year 8 Second edition
ISBN 978-1-108-46627-1 © Palmer et al. 2018
Cambridge University Press
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