Checking understanding of similarity | Maths | Quizalize & Oak National Academy

Starter quiz

Two shapes are ______ if the only difference between them is their size. Their side lengths are in the same proportions.
- 'similar' ✓
The __________ is the multiplier between similar shapes that describes how large one shape is compared to the other.
- centre of enlargement
- line of reflection
- scale factor ✓
- vector
Which rectangle is a correct enlargement of of rectangle R?
- A
- B ✓
- C
Triangle A has been enlarged by a scale factor of 2 to get triangle B. Match each unknown length from triangle B with its size.
- $a\text{ }$ cm
  
  ⇔
  
  8 cm ✓
- $b\text{ }$ cm
  
  ⇔
  
  6 cm ✓
- $c\text{ }$ cm
  
  ⇔
  
  10 cm ✓
A square has length 8 cm. It is enlarged by a scale factor of $1\over{2}$ . The side length of its image is ______ cm.
- '4' ✓
Each angle in an equilateral triangle is 60°. If an equilateral triangle is enlarged by a scale factor of 2, each of its angles will be ______°.
- '60' ✓

Exit quiz

A property of a shape is ______ if that property has not changed after the shape is transformed.
- 'invariant' ✓
A shape is being enlarged by a scale factor of 4. One vertex is 3 cm from the centre of enlargement. Its corresponding vertex on the image will be ______ cm from the centre of enlargement.
- '12' ✓
Sofia is enlarging the shape by a scale factor of 2. Which vertex has Sofia plotted incorrectly?
- A
- B ✓
- C
A parallelogram is enlarged by a scale factor of 3. Which of the following measurements will remain invariant?
- The angles. ✓
- The length of its base.
- The length of its height.
- The length of its slope.
The two triangles are similar. The value of $x$ is ______.
- '18' ✓
A triangle has a base of 6 m and height of 2 m. A similar triangle, in the same orientation, has a base of 15 feet. Its height is ______ feet.
- '5' ✓

Worksheet

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Lesson Details

Key learning points

An enlargement means a change in size.
The lengths of the lines may change when enlarged.
The angles inside an object do not change when enlarged.
When an object is enlarged, the image is similar.

Common misconception

When a pair of similar shapes are not in the same orientation, pupils may select an incorrect pair of lengths to calculate the scale factor.

Encourage pupils to take a systematic approach to locating pairs of corresponding lengths by looking for the longest edge in each shape, then the second longest, third longest, etc.

Keywords

Object - The object is the starting figure before a transformation has been applied.
Image - The image is the resulting figure after a transformation has been applied.
Similar - Two shapes are similar if the only difference between them is their size. Their side lengths are in the same proportions.
Scale factor - Scale factor is the multiplier between similar shapes that describes how large one shape is compared to the other.
Invariant - A property of a shape is invariant if that property has not changed after the shape is transformed.