Ch 9.7Perimeters and Similarity

Standard 11.0Students determine how changes in dimensions

affect the perimeter of common geometric figures.

Learning Target:I will be able to identify and use proportional relationships of similar triangles.

Ch 9.7

Ch 9.7

Use a Scale Factor to Find Perimeter

If ABCDE ~ RSTUV, find the scale factor of ABCDE to RSTUV and the perimeter of each polygon.

Ch 9.7

Use a Scale Factor to Find Perimeter

The scale factor ABCDE to RSTUV is or . ___AEVU

__47

Write a proportion to find the length of DC.

Since DC AB and AE DE, the perimeter of ABCDE is 6 + 6 + 6 + 4 + 4 or 26.

Write a proportion.

4(10.5)= 7 ● DC Cross Products Property

6 = DC Divide each side by 7.

Ch 9.7

Use a Scale Factor to Find Perimeter

Use the perimeter of ABCDE and scale factor to write a proportion. Let x represent the perimeter of RSTUV.

Theorem 7.1

Substitution

4x = (26)(7) Cross Products Property

x = 45.5 Solve.

Ch 9.7

Answer: The perimeter of ABCDE is 26 and the perimeter of RSTUV is 45.5.

A. LMNOP = 40, VWXYZ = 30

B. LMNOP = 32, VWXYZ = 24

C. LMNOP = 45, VWXYZ = 40

D. LMNOP = 60, VWXYZ = 45

If LMNOP ~ VWXYZ, find the perimeter of each polygon.

Ch 9.7