1. Ratios, Rates and Percents
Lesson 22
Ratios, Rates and Percents
Perimeter and Circumference

2. Warm-Up Find the circumference of each circle. Round each
answer to the nearest tenth. Use 3.14 for .
2 inches
5 meters

3. Perimeter and Circumference
Target:
Find the perimeter of combined shapes.

5. Example 1a Find the perimeter of the shape.
Find the circumference of the half-circle.
Circumference = π × diameter
Find circumference of whole circle × 4 = m
Find the half-circle circumference ÷ 2 = 6.28 m
Add the length of the diameter = m
The perimeter is meters.

6. Example 1b Find the perimeter of the shape.
Find the perimeter around the rectangle = 16 in
Find the perimeter around the triangle = 8 in
Add the two perimeters together = 24 in
The perimeter is 24 inches.

7. Example 2 Find the height of the rectangle. The perimeter of the
shape is 34 feet.
Find the known perimeter = 30 ft
Find the difference between
34 and – 30 = 4 ft
The height of the rectangle is 4 feet.

8. Exit Problems
Find the perimeter of each shape.

9. Communication Prompt
Think of an object in your home or yard that is a combination of shapes. How would you find the perimeter of the shape?