New
New
Year 7

# Describing an enlargement

I can understand the minimum information required to describe an enlargement

New
New
Year 7

# Describing an enlargement

I can understand the minimum information required to describe an enlargement

## 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.

### 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.

### 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.

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).

## Starter quiz

### 6 Questions

Q1.
Enlargement is a transformation that causes a change of __________.
Q2.
Two shapes are similar if the only difference between them is
their angles
one side
one angle
Q3.
Enlarging a shape means the shape will always get smaller.
True
Q4.
Which properties are not invariant when a shape is enlarged?
angles
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
20.8 cm

## Exit quiz

### 6 Questions

Q1.
__________ factor is the multiplier between similar shapes that describes how large the image is compared to the object.
Q2.
The of enlargement is the point from which a shape is enlarged.
Q3.
The object has been enlarged to create the image. What is the scale factor?
3
4
6
20
Q4.
The object has been enlarged to create the image. What is the value of $$x$$?
3
12
Correct answer: $$1\over10$$
The object has been enlarged to create the image. What is the value of $$x$$?