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.- cm⇔8 cm ✓
- cm⇔6 cm ✓
- cm⇔10 cm ✓
- A square has length 8 cm. It is enlarged by a scale factor of . 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 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
Presentation
Video
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.