year 8 maths

130 Chapter 3 Measurement and Pythagoras’ theorem
3C Area
REVISION
Area is a measure of surface and is often referred to as the amount of space contained inside a
two-dimensional space. Area is measured in square units and the common metric units are square
millimetres (mm 2 ) , square centimetres (cm 2 ) , square metres (m 2 ) , square kilometres (km 2 ) and hectares (ha) .
The hectare is often used to describe area of land, since the square kilometre for such areas is considered
to be too large a unit and the square metre too small. A school football oval might be about
1 hectare, for example, and a small forest might be about 100 hectares.
Let’s start: Squares of squares
Consider this enlarged drawing of one square centimetre
divided into square millimetres.
• How many square millimetres are there on one edge of
the square centimetre?
• How many square millimetres are there in total in
1 square centimetre?
• What would you do to convert between mm 2 and cm 2 or
cm 2 and mm 2 . Why?
• Can you describe how you could calculate the number
of square centimetres in 1 square metre and how many
square metres in 1 square kilometre? What diagrams
would you use to explain your answer?
1 cm = 10 mm
1 cm =
10 mm
Key ideas
■ The common metric units for area include: ×1000 2 ×100 2 ×10 2
• square millimetres (mm 2 )
= 1000000 = 10000 = 100
• square centimetres (cm 2 )
• square metres (m 2 )
km 2 m 2 cm 2 mm 2
• square kilometres (km 2 )
÷1000 2 ÷100 2 ÷10 2
• hectares (ha) ×10 000
= 1000000 = 10000 = 100
ha
m 2
÷10 000
■ Area of squares, rectangles and triangles
2
• Square A = S × S = S
s
• Rectangle A = l × b = lb
b
l
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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