year 8 maths

4E
Terminating decimals, recurring decimals and rounding
225
Example 16 Rounding decimals
Round each of the following to the specified number of decimal places.
a 15.35729 ( three decimal places)
b 4.86195082 ( four decimal places)
SOLUTION
EXPLANATION
a 15.35729 ≈ 15.357 (to 3 d.p.) Critical digit is 2 , which is less than 5 .
Rounding digit remains the same.
b 4.86195082 ≈ 4.8620 (to 4 d.p.) Critical digit is 5 , therefore increase rounding
digit by 1 . There is a carry-on effect, as the
rounding digit was a 9 .
Example 17 Rounding recurring decimals
Write
SOLUTION
3
as a decimal, correct to two decimal places.
7
EXPLANATION
3
7 = 0.43 (to 2 d.p. ) 0. 4 2 8
7⟌3. 3 0 2
0 6
0
4
0
Exercise 4E
REVISION
UNDERSTANDING AND FLUENCY
1–6, 7–8(½), 9 3–6, 7–8(½), 9, 10 5, 6, 7–8(½), 9, 10
1 State whether the following are terminating decimals (T) or recurring decimals (R).
a 5.47
b 3.15415 . …
c 8.6 .
d 7.1834
e 0.333
f 0.5 . 34 .
g 0.5615
h 0.32727…
2 Express the following recurring decimals using the convention of dots or a bar to indicate the start and
finish of the repeating cycle.
a 0.33333…
b 6.21212121…
c 8.5764444…
d 2.135635635…
e 11.2857328573…
f 0.003523523…
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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