year 8 maths

128 Chapter 3 Measurement and Pythagoras’ theorem
PROBLEM-SOLVING AND REASONING
8–10, 14 9–12, 14, 15
11–13, 15–17
8 A water tank has a diameter of 3.5 m . Find its circumference, correct to one decimal place.
9 An athlete trains on a circular track of radius 40 m and jogs 10 laps each day, 5 days a week.
How far does he jog each week? Round your answer to the nearest whole number of metres.
10 These shapes are semicircles. Find the perimeter of these shapes including the straight edge and
round the answer to two decimal places.
a 25 cm b
c
4.8 m
12 mm
11 Calculate the perimeter of these diagrams, correct to two decimal places.
a
b
c
14 m
45° 2 cm
8 cm
12 Calculate the perimeter of these shapes, correct to two decimal places.
a
b
c
4 cm
9 m
10 m
5 m
13 Here are some students’ approximate circle measurements. Which students have incorrect
measurements?
r
C
Mick 4 cm 25.1 cm
Svenya 3.5 m 44 m
Andre 1.1 m 13.8 m
14 Explain why the rule C = 2πr is equivalent to (i.e. the same as) C = πd .
15 It is more precise in mathematics to give ‘exact’ values for circle calculations in terms of π .
For example, C = 2 × π × 3 gives C = 6π . This gives the final exact answer and is not written as a
rounded decimal. Find the exact answers for Question 5 in terms of π .
16 Find the exact answers for Question 12 in terms of π .
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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