**Definition of Perimeter**

- Perimeter is the distance around a polygon.

**Examples of Perimeter**

- The perimeter of the rectangle shown is AB + BC + CD + DA = 8 + 5 + 8 + 5 = 26 units

- Perimeter of a rectangle can also be found using the formula 2(
*l + w*), where*l*is the length and*w*is the width.

**Solved Example on Perimeter**

ABC is an equilateral triangle and the perimeter of triangle ABC is 12 in. Find the measure of each side.

Choices:

A. 36 in.

B. 4 in.

C. 12 in.

D. 6 in.

Correct Answer: B

Solution:

Step 1:In triangle ABC, AB = BC = CA

Step 2:Let AB = BC = CA =xin.

Step 3:Perimeter of ΔABC = AB + BC + CA

Step 4:AB + BC + CA = 12

Step 5:x + x + x= 12 [Substitute AB = BC = CA =x.]

Step 6:3x= 12 [Combine like terms.]

Step 7:[Divide each side by 3.]

Step 8:x= 4 [Simplify.]

Step 9:AB = BC = CA = 4 in.

Step 10:So, the measure of each side is 4 in.

**Related Terms for Perimeter**

- Polygon