year 8 maths

134 Chapter 3 Measurement and Pythagoras’ theorem
Example 8
6 Find the area of these composite shapes using addition or subtraction.
a
b
9 m
4 m
5 m
c
14 cm
5 m
8 cm
10 m
3 m
d
16 cm
e
10 km
f
7 cm
6 km
7 km
2 km
3 cm
6 mm
4 mm
PROBLEM-SOLVING AND REASONING
7, 8, 13 7–10, 13, 14
7–15
7 Use your knowledge of area units to convert these measurements to the units shown in the
brackets.
a 0.2 m 2 (mm 2 ) b 0.000043 km 2 (cm 2 ) c 374 000 cm 2 (km 2 )
d 10 920 mm 2 (m 2 ) e 0.0000002 ha (cm 2 ) f 6 km 2 (ha)
8 Find the area of these composite shapes. You may need to determine some side lengths first.
Assume that all angles that look right angled are 90° .
a 9 cm
b 14 m
c
3 m
6 cm
3 m
3 m
3 m
20 m
15 km
12 km
9 Find the side length of a square if its area is:
a 36 m 2 b 2.25 cm 2
10 a Find the area of a square if its perimeter is 20 m .
b Find the area of a square if its perimeter is 18 cm .
c Find the perimeter of a square if its area is 49 cm 2 .
d Find the perimeter of a square if its area is 169 m 2 .
11 A triangle has area 20 cm 2 and base 4 cm . Find its height.
12 Paint costs $12 per litre and can only be purchased in a full number of litres. One litre of paint
covers an area of 10 m 2 . A rectangular wall is 6.5 m long and 3 m high and needs two coats of
paint. What will be the cost of paint for the wall?
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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