1. Ch 9.7 Perimeters and Similarity
Learning Target:
I will be able to identify and use proportional relationships of similar triangles.
Standard 11.0
Students determine how changes in dimensions affect the perimeter of common geometric figures.

2. Ch 9.7
Concept

3. 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.
Example 4

4. Ch 9.7 The scale factor ABCDE to RSTUV is or . AE VU 4 7
Use a Scale Factor to Find Perimeter
The scale factor ABCDE to RSTUV is or
___ AE VU __ 4 7
Write a proportion to find the length of DC.
Write a proportion.
4(10.5) = 7 ● DC Cross Products Property
6 = DC Divide each side by 7.
Since DC  AB and AE  DE, the perimeter of ABCDE is or 26.
Example 4

5. 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.
Answer: The perimeter of ABCDE is 26 and the perimeter of RSTUV is 45.5.
Example 4

6. Ch 9.7 If LMNOP ~ VWXYZ, find the perimeter of each polygon.
A. LMNOP = 40, VWXYZ = 30
B. LMNOP = 32, VWXYZ = 24
C. LMNOP = 45, VWXYZ = 40
D. LMNOP = 60, VWXYZ = 45
Example 4