year 8 maths

502 Chapter 8 Transformations and congruence
Example 12 Finding a missing length
Given that these pairs of triangles are similar, find the
value of the pronumerals.
5
4
y
15
9
x
SOLUTION
Scale factor = 15 5 = 3
x = 4 × 3 = 12
y = 9 ÷ 3 = 3
EXPLANATION
First find the scale factor.
Multiply or divide by the scale factor to find the
values of the pronumerals.
Exercise 8G
EXTENSION
UNDERSTANDING AND FLUENCY
1–4 2–4
3, 4
1 Write a similarity statement for these pairs of similar triangles; for example, △ABC ||| △DEF .
Be careful with the order of letters and make sure each letter matches the corresponding vertex.
a
C
D b
B E
7 cm 6 cm
12 cm
A
C
D
14 cm
F
A
B
F
E
c
B
4 m
C
D
d
B
F
A
5 m
F
15 m
12 m
E
C
5 mm
A
D
2 mm
E
2 For the pairs of triangles in Question 1 , which of the four similar triangle tests would be used to show
their similarity? See the Key ideas for a description of each test. There is one pair for each test.
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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