Similar Shapes

Similar Shapes – Demonstration

This resource provides animated demonstrations of the mathematical method.

Check animations and delete slides not needed for your class.

What’s the same & what’s different, with these pairs of shapes?

These shapes are similar: one of the shapes is an enlargement of the other.

What’s the same & what’s different, with these pairs of shapes?

These shapes are similar: one of the shapes is an enlargement of the other.

When we enlarge shapes, do the interior angles of the shape change?

When we enlarge shapes, interior angles don’t change, only the side lengths.

How has each shape been enlarged?

4 metres

8 metres

2 metres
6 metres

35°

35°

2 metres

4 metres

When we enlarge shapes, interior angles don’t change, only the side lengths.

How has each shape been enlarged?

4 metres

8 metres

2 metres
6 metres

35°

35°

2 metres

4 metres

Side Lengths × 2

Scale Factor of Enlargement: 2

When we enlarge shapes, interior angles don’t change, only the side lengths.

How has each shape been enlarged?

4 metres

8 metres

2 metres
6 metres

35°

35°

2 metres

4 metres

Side Lengths × 2

Scale Factor of Enlargement: 2

Side Lengths × 3

Scale Factor of Enlargement: 3

These are similar shapes.

What is the scale factor of enlargement?

DEMO

4 cm

Not to scale.

Similar Shapes

8 cm

These are similar shapes.

What is the scale factor of enlargement?

DEMO

4 cm

Not to scale.

Similar Shapes

8 cm

8
4= 2

Are these shapes similar?

4 cm

8 cm

8 cm

14 cm

Are these shapes similar?

4 cm

8 cm

8 cm

14 cm

We can compare corresponding sides.

Are these shapes similar?

4 cm

8 cm

8 cm

14 cm

We can compare corresponding sides.

Are these shapes similar?

4 cm

8 cm

8 cm

14 cm

We can compare corresponding sides.

Are these shapes similar?

4 cm

8 cm

8 cm

14 cm

We can compare corresponding sides.

The length has

a smaller scale factor of enlargement than the width.

The shapes are not similar.

Multiple Choice

Are the following similar? Why or why not?

• Yes

• No, the corresponding angles are not equal.

• No, the ratios of the corresponding sides are not equal.

Multiple Choice

Which statement is true?

• All squares are similar

• All hexagons are similar

• All scalene triangles are similar

• All similar figures are the same shape and size

First identify the two corresponding sides.

​Then find the scale factor.

Either multiply or divide by SF to find the missing length.

​Finding the missing length

Multiple Choice

Find the length of x

• x = 1

• x = 2

• x = 7

• x = 1/7

Multiple Choice

• 26

• 22

• 12

• 15

Multiple Choice

Two objects that are the same shape but not the same size are _______.

• Congruent

• Vertical

• Similar

• Complementary 

Multiple Choice

All corresponding sides are proportional (same ratio) in similar figures.

• True

• False

Multiple Choice

Find x.

• 6.6

• 4.5

• 5.4

• 7.2

Multiple Choice

Triangle ABC and XYZ are similar.  Use your knowledge of scale factor to find the length of X.

• 20

• 25

• 100

• 40

Multiple Choice

The following shapes are similar, the smaller one is the original shape, what is the scale factor?

• 8:12

• 3:2

• 4:8

• 6:12

Multiple Choice

• 4

• 6

• 8

• 10

Poll

How did you find todays lesson?