**Similar triangles (part 2)**

Starter

Triangles ABC and DEF are similar. Work out the exact length of DE.

Give your answer in the form

a

b

, where

a

and

b

are integers.

Activity

Complete the worksheet.

**L.O. - To find missing lengths in connected similar triangle diagrams.**

Examples

Examples

S.f. = 1.5

x + 5 = 7.5

x = 2.5 cm

S.F. = 1

6 x 1 = 10

AB = 10 cm

2

3

2

3

Activity

Activity

S.F = 2

17 x 2 = 40

x = 40 - 17 = 23

3

8

3

8

3

8

3

8

3

8

S.F = 3.5

5 x 3.5 = 17.5

x = 17.5 cm.

Activity

Complete the worksheet.

A

B

C

4 cm

8 cm

D

E

F

10 cm

Starter

Triangles ABC and DEF are similar. Work out the exact length of DE.

Give your answer in the form

a

b

, where

a

and

b

are integers.

A

B

C

4 cm

8 cm

D

E

F

10 cm

80

or 4 5 .

5 5 .

**Activities**

**Activity**

Answers

Answers

**Key**

Examples

Examples

**Worked**

Example

Example

**Worked**

Example

Example

Starter

Triangles ABD and BCD are similar. Work out the exact length of AB.

Give your answer in the form

a

b

, where

a

and

b

are integers.

A

B

C

4 cm

6 cm

D

Starter

Triangles ABD and BCD are similar. Work out the exact length of AB.

Give your answer in the form

a

b

, where

a

and

b

are integers.

A

B

C

4 cm

6 cm

D

BC = 4 + 6 = 52

BC = 52 = 2 13

ratio of lengths =4:6 = 2:3

so s.f. = 1.5

1.5 x 2 13 = 3 13

2

2

2