1. Objective: To find the perimeters and areas of similar figures.
Chapter 8 Lesson 6
Objective: To find the perimeters and areas of similar figures.

2. Perimeters and Areas of Similar Figures
Theorem 8-6  
Perimeters and Areas of Similar Figures
If the similarity ratio of two similar figures is    , then (1) the ratio of their perimeters is   and (2) the ratio of their areas is    .

3. Example 1: Finding Ratios in Similar Figures
The trapezoids are similar. The ratio of the lengths of corresponding sides is
Find the ratio (smaller to larger) of the perimeters.
Find the ratio (smaller to larger) of the areas.

4. Example 2: Finding Ratios in Similar Figures
Two similar polygons have corresponding sides in the ratio 5 : 7. Find the ratio of their perimeters.

5. Example 3: Finding Ratios in Similar Figures
Two similar polygons have corresponding sides in the ratio 5 : 7. Find the ratio of their areas.

6. Example 4: Finding Areas Using Similar Figures
The area of the smaller regular pentagon is about 27.5 cm2. Find the area A of the larger regular pentagon.
All regular pentagons are similar.
Ratio of the lengths of the corresponding
sides is  
The ratio of the areas is
172 cm2

7. Example 5: Finding Areas Using Similar Figures
The corresponding sides of two similar parallelograms are in the ratio ¾. The area of the larger parallelogram is 96 in.2. Find the area of the smaller parallelogram.
Area Ratio

8. Example 6: Finding Similarity and Perimeter Ratios
The areas of two similar triangles are 50 cm2 and 98 cm2. What is the similarity ratio? What is the ratio of their perimeters?
Find the similarity ratio a : b.
                                                                          

9. Example 7: Finding Similarity and Perimeter Ratios
The areas of two similar rectangles are 1875 ft2 and 135 ft2. Find the ratio of their perimeters.

10. Assignment
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