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Year 7

Describing an enlargement

I can understand the minimum information required to describe an enlargement

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New
New
Year 7

Describing an enlargement

I can understand the minimum information required to describe an enlargement

Download all resources
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Share activities with pupils
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Lesson details

Key learning points

  1. The scale factor is the multiplier.
  2. The centre of enlargement defines where the image will be placed in relation to the object.
  3. The object and enlarged image have the same orientation for positive scale factors.

Keywords

  • Centre of enlargement - The centre of enlargement is the point from which a shape is enlarged.

  • Scale factor - A scale factor is the multiplier between similar shapes that describes how large one shape is compared to the other.

Common misconception

Pupils may want to use division instead of fractional scale factors.

Dividing by 2 gives the same result as multiplying by a half. However, the scale factor is defined as a multiplier, not a divisor.

Describe the change of size colloquially as well as mathematically during examples (e.g. "the image is twice the size of the object", "the image is half the size of the object").
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Starter quiz

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6 Questions

Q1.
Enlargement is a transformation that causes a change of __________.
Correct Answer: size
Q2.
Two shapes are similar if the only difference between them is
their angles
one side
one angle
Correct answer: their size
Q3.
Enlarging a shape means the shape will always get smaller.
True
Correct answer: False
Q4.
Which properties are not invariant when a shape is enlarged?
Correct answer: side lengths
angles
Correct answer: position
Q5.
Sam is going to triple the size of a rectangle. What will happen to the angles?
They will all triple in size.
Correct answer: They will all stay the same size.
They will all become a third of the size.
Q6.
Lucas' rectangle has a length of 7 cm and a width of 2.6 cm. A similar rectangle has a length of 28 cm. What will its width be?
1.3 cm
2.6 cm
Correct answer: 10.4 cm
20.8 cm

Exit quiz

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6 Questions

Q1.
__________ factor is the multiplier between similar shapes that describes how large the image is compared to the object.
Correct Answer: Scale, scale
Q2.
The of enlargement is the point from which a shape is enlarged.
Correct Answer: centre
Q3.
The object has been enlarged to create the image. What is the scale factor?
An image in a quiz
3
4
Correct answer: 5
6
20
Q4.
The object has been enlarged to create the image. What is the value of $$x$$?
An image in a quiz
3
12
Correct answer: 15
20
Q5.
The object has been enlarged to create the image. What is the scale factor?
An image in a quiz
Correct answer: $$1\over10$$
5
5.5
10
Q6.
The object has been enlarged to create the image. What is the value of $$x$$?
An image in a quiz
Correct answer: 3.2
5.5
9
320