Year 9

Year 9

# Similar triangles

## Lesson details

### Key learning points

1. In this lesson, we will learn to define similarity and apply your understanding to similar triangles. We will also draw an enlargement.

### Licence

This content is made available by Oak National Academy Limited and its partners and licensed under Oak’s terms & conditions (Collection 1), except where otherwise stated.

## Video

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## Worksheet

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## Starter quiz

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### 5 Questions

Q1.
Which of these is an incomplete description of an enlargement?
Shape 3 has been enlarged about point (1, 3) with scale factor -2
Correct answer: Shape A has been enlarged by scale factor -2
Shape B has been enlarged by scale factor -2, about (1,3)
Q2.
Which of the following is the correct description of the below enlargement?
Scale factor 2.5, centre (1,2)
Shape A has been enlarged by scale factor 2
Correct answer: Shape A has been enlarged by scale factor 2.5, centre (1, 2)
Shape A has been enlarged by scale factor 5, centre (2, 1)
Q3.
A shape has been enlarged and the image has a larger area and is in a different orientation to the object. Which of the following options could describe this enlargement?
Correct answer: The object has been enlarged by scale factor -2, centre (1,0)
The object has been enlarged by scale factor 0.2, centre (1,0)
The object has been enlarged by scale factor 2, centre (1, 0)
The object has been enlarged by scale factor 2.2, centre (1,0)
Q4.
A shape has been enlarged and the image has a smaller area than the object and is in the same orientation. Which of the following options could describe this enlargement?
The object has been enlarged by scale factor -2, centre (1,0)
Correct answer: The object has been enlarged by scale factor 0.2, centre (1,0)
The object has been enlarged by scale factor 2, centre (1, 0)
The object has been enlarged by scale factor 2.2, centre (1,0)
Q5.
A shape has been enlarged and the image has a smaller area than the object and has a different orientation. Which of the following options could describe this enlargement?
Correct answer: The object has been enlarged by scale factor -0.2, centre (1,0)
The object has been enlarged by scale factor -2, centre (1, 0)
The object has been enlarged by scale factor 0.2, centre (1,0)
The object has been enlarged by scale factor 2.2, centre (1,0)

## Exit quiz

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### 5 Questions

Q1.
Fill in the gap: if one shape is an enlargement of another, then these shapes are called ________ shapes.
congruent
opposite
the same
Q2.
Fill in the gap: in all similar shapes, corresponding __________ are equal.
Areas
Corners
Sides
Q3.
Fill in the gap: corresponding sides of similar shapes are all enlarged by the same __________.
Amount
Bigger
Multiplication