Recognise and Describe Enlargements

In this activity, we will recognise and describe enlargements!

 

We have looked at three other transformations - reflections, rotations and translations.

Enlargements are the easiest to spot as they change size!    

Let's look at them - you can make notes here to help you describe them!

 

 

You can see they are similar shapes - same size angles, but sides multiplied by a scale factor of 2.

 

We find the scale factor by dividing the enlarged side by the side from the shape being enlarged.

Scale factor = 4 ÷ 2 = 2

It means the sides on the enlargement are 2 times longer.

 

We would describe the transformation as:

An enlargement by scale factor 2

 

Let's look at another one!

 

Example

Describe the transformation of shape A, below.

 

 

Answer

We can see the base of shape A = 1 

The base of the transformation = 3

 

The scale factor = 3 ÷ 1 = 3

To check, we can look at the heights.

Height of A = 2 and the height of the transformation is 6 (6 ÷ 2 = 3)

We can say this is an 

Enlargement by scale factor 3

 

Let's introduce a centre of enlargement.

 

Example

Enlarge the shape A by scale factor 2, from the centre of enlargement X. 

 

 

Answer

We take each vertex (corner) and look at the distance.

 

 

This one is 1 right and 1 down from the centre (X)

To enlarge, it we multiply the distance by the scale factor (2) 

We go 1 x 2 = 2 right and 1 x 2 = 2 down, x is the new vertex.

Let's plot another corner!

 

2 right and 2 up (x 2 because of the scale factor)

Gives us 4 right and 4 up

 

Last one!

 

 3 right and 1 down (x 2)

Gives us 6 right and  2 down 

 

Finally, join up the vertices!

 

An enlargement of scale factor 2 from the centre X

 

Let's try some questions!