CIRCUMFERENCES AND PERIMETERS

SIMPLE

Concept: Perimeter is a measure of the distance around the edge of any flat shape. To find the perimeter of a polygon, add the lengths of its sides. The perimeter of a circle is called the circumference. The formula used to find the circumference of a circle is:. Note: The Pythagorean Theorem is often necessary to solve these problems (a2 + b2 = c2). Some figures may be made up of several shapes. To find the perimeter of a combined figure, find the perimeter of each of the parts and add the results. Some problems may require multiple steps, and/or variations on the Steps listed below.

Steps for Finding the Perimeter and Circumferences

Step 1 | Divide the figure into simple shapes. For each shape work Steps 2, 3, and 4.
Step 2 | Choose the proper formula for the first shape in the problem.
Step 3 | Substitute the values.
Step 4 | Solve.
Step 5 | Repeat Steps 2, 3, and 4 as needed.
Step 6 | Combine perimeters.
Step 7 | Write the final answer.

Example 1 Solve for b given perimeter =19, a=7, s1=2, s2=2

Step 1 | Choose the proper formula for the figure in the problem. | s1 + s2 + a + b = P
Step 2 | Substitute the values. | 2 + 2 + 7 + b = 19
Step 3 | Solve. | 2 + 2 + 7 + b = 19 11 + b = 19 11 + b = 19 -11 -11 0 + b = 8 b = 8
Step 4 | Write final answer. | b = 8

Example 2 Solve for radius given C = 50.24 and pi = 3.14

Step 1 | Choose the proper formula for the figure in the problem. |
Step 2 | Substitute the values. | 50.24 = 3.14 x d
Step 3 | Solve. | 50.24 = 3.14 x d 50.24 = 3.14 x d 3.14 3.14 16 = 1 x d 16 = d
Step 4 | Write final answer. | 16 = d