2. Essential Understanding
 You can use ratios to compare the perimeters and
areas of similar figures
 Students will be able to find the perimeters and
areas of similar figures

3. Perimeters and Areas of
Similar Figures
 If the scale factor of two similar figures is a/b, then
 The ratio of their perimeters is a/b
 The ratio of their areas is a2/b2

4. Finding Ratios
 Two similar polygons have corresponding sides in
the ratio 5:7
 What is the ratio (larger to smaller) of their
perimeters?
 What is the ratio (larger to smaller) of their areas?

5. Finding Area
 The scale factor of two similar parallelograms is ¾.
The area of the larger parallelogram is 96 in2. What
is the area of the smaller parallelogram?

6. Finding Area
 The area of the smaller regular hexagon is about 127.3
ft2. What is the best approximation for the area of the
larger regular hexagon?

7. Applying Area
 The scale factor of the dimensions of two similar
pieces of window glass is 3:5. The smaller piece
costs $2.50. How much should the larger piece
cost?

8. Applying Area

9. Finding Perimeter
 The areas of two similar rectangles are 1875 ft2 and
135 ft2. What is the ratio of their perimeters?

10. Perimeter

11. Homework
 Pg. 638
 # 9 – 18, 20 – 28 even, 46
 16 problems