Bell Work

M

N L S

R T

Write a congruence statement.

∆MNL ≅ ∆SRT

• Two objects are similar if they are the same shape but different sizes.

Similar Polygons

Example:

Is the pair of polygons similar? Explain your answer.

5 m 8 m

10 m

13 m

OR13

8

10

5

13

10

8

5

5(13) = 10(8)

65 = 80

NO

5(13) = 8(10)

65 = 80

NO

Example:

Is the pair of polygons similar? Explain your answer.

4 yd 3 yd

6 yd4.5 yd

OR5.4

3

6

4

5.4

6

3

4

4(4.5) = 6(3)

18 = 18

YES

4(4.5) = 6(3)

18 = 18

YES

15 ft 9 ft

21 ft

12 ft

Yes

No

Are the polygons similar? You must be able to justify your answer. (Shapes not drawn to scale.)

10 m

8 m

2.5 m

2 m

Yes

No

Are the polygons similar? You must be able to justify your answer. (Shapes not drawn to scale.)

15 yd

6 yd

15 yd

37.5 yd

Yes

No

Are the polygons similar? You must be able to justify your answer. (Shapes not drawn to scale.)

Example:

Find the value of x in the pair of similar polygons.

15 cmx

6 cm

8 cm

10 cm

OR10

615

x 106

15 x

15(10) = 6x

150 = 6x

25 cm = x

15(10) = 6x

150 = 6x

25 cm = x

You try:

Find the value of y in the pair of similar polygons.

y

15 in

5 in

7.5 in

15(5) = 7.5x

75 = 7.5x

10 in = x

55.7

15 y

15(5) = 7.5x

75 = 7.5x

10 in = x

5

5.715

yOr

25 ft 25 ft

18 ft

17.5 ft

w

Find the measure of the missing value in the pair of similar polygons. (Shapes not drawn to scale.)

12.6 ft

A

B

C

D

18ft

450ft

.07 ft

17 m4.25 m

4 mx

Find the measure of the missing value in the pair of similar polygons. (Shapes not drawn to scale.)

16m

68ft

A

B

C

D

16.25m

18.06ft

11 mm 38.5 mm

6 mmy

Find the measure of the missing value in the pair of similar polygons. (Shapes not drawn to scale.)

21 mm

33.5mm

A

B

C

D

66mm

70.58mm

Scale Factor

• When you compare corresponding measurements of proportional objects, you get a ratio.

• This ratio is called the scale factor.

What is the scale factor from the larger shape to the smaller one?

Practice:Similar Polygons

Worksheet