A transformation is a process that may change the size, orientation or position of a shape.

Enlargement is a transformation that causes a change of size.

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

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

Enlargement using a negative scale factor

Maths

In this unit, pupils enhanced their understanding of enlargement. In this future unit, pupils investigate the effect of an enlargement on the perimeter and area of a 2-D shape and the volume of a 3-D shape. 

In the prior unit, pupils learnt about the different types of transformations. In this unit, pupils' knowledge is extended as negative scale factors are considered as are multiple transformations.

Further transformations

When the scale factor of an enlargement is negative, the image is a rotation of {{}}° of the object.

Which diagram shows an enlargement by a negative scale factor?

Yes, any enlargement by a scale factor less than 1 gives a smaller image.

No, the scale factor could be negative so the image will be larger.

No, a fraction may have an absolute value greater than 1 such as $$\frac{3}{2}$$

Laura says, "When you enlarge an object by a fractional scale factor, the image is always smaller than the object." Is Laura correct? Justify your answer.

Shape A is enlarged to give shape B. The scale factor of this enlargement is {{}}.

Shape A is enlarged to give shape B. The centre of enlargement is at the {{}}.

An enlargement scale factor $$\frac{3}{2}$$, centre $$(4, 4)$$

An enlargement scale factor $$-\frac{3}{2}$$, centre $$(0, 0)$$

An enlargement scale factor $$-\frac{5}{2}$$, centre $$(4, 4)$$

An enlargement scale factor $$-\frac{5}{2}$$, centre $$(0, 0)$$

An enlargement scale factor $$\frac{5}{2}$$, centre $$(4, 4)$$

Shape A is transformed to give shape B. Describe the transformation.

A transformation is a process that may change the {{}}, orientation or position of a shape.

Shape B is enlarged to give shape A. What is the scale factor of this enlargement?

Three Oak pupils enlarge the same shape. Whose diagrams are incorrect?

Shape B is enlarged to give shape A. The centre of the enlargement is at (-3, {{}}).

An enlargement scale factor $$\frac{1}{2}$$, centre (0,0)

An enlargement scale factor $$\frac{1}{2}$$, centre (-1, -1)

An enlargement scale factor $$\frac{1}{2}$$, centre (0, -1)

An enlargement scale factor $$2$$, centre (0, 0)

An enlargement scale factor $$\frac{1}{2}$$

Describe the transformation that maps shape A onto shape B.

This lesson will soon be taken down.

Enlargement using a negative scale factor

Lesson outcome