year 8 maths

3B
Circumference of circles
127
Exercise 3B
REVISION
UNDERSTANDING AND FLUENCY
1–7 4, 5(½), 6, 7
5(½), 6, 7
1 Evaluate the following using a calculator and round to two decimal places.
a π × 5 b π × 13 c 2 × π × 3 d 2 × π × 37
2 Write down the value of π , correct to:
a one decimal place b two decimal places c three decimal places
3 Name the features of the circle shown at right.
a
b
4 A circle has circumference (C ) 81.7 m and diameter (d ) 26.0 m , correct to one decimal place.
Calculate C ÷ d . What do you notice?
c
Example 4
5 Find the circumference of these circles, correct to two decimal places. Use a calculator for the
value of pi.
a
b
c
2 mm
18 m
39 cm
d
e
f
5 cm
4 m
7 km
Example 5a
6 Calculate the circumference of these circles using π = 3.14 .
a
b
100 cm
20 m
c
3 km
Example 5b
7 Calculate the circumference of these circles using π = 22 7 .
a
b
c
7 mm
21 cm
70 m
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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