How to Find the Perimeter of a Triangle

Step-by-Step Guide

1. 1

   Step 1: Remember the formula for finding the perimeter of a triangle.

   For a triangle with sides a, b and c, the perimeter P is defined as:
   P = a + b + c.
   
   What this formula means in simpler terms is that to find the perimeter of a triangle, you just add together the lengths of each of its 3 sides.
2. 2

   Step 2: Look at your triangle and determine the lengths of the three sides.

   In this example, the length of side a = 5, the length of side b = 5, and the length of side c =
   5.
   
   This particular example is called an equilateral triangle, because all three sides are of equal length.
   
   But remember that the perimeter formula is the same for any kind of triangle. , In this example, 5 + 5 + 5 =
   15.
   
   Therefore, P =
   15.
   
   In another example, where a = 4, b = 3, and c=5, the perimeter would be:
   P = 3 + 4 + 5, or
   12. , If the sides of the triangle are measured in centimeters, then your answer should also be in centimeters.
   
   If the sides are measured in terms of a variable like x, your answer should also be in terms of x.
   
   In this example, the side lengths are each 5cm, so the correct value for the perimeter is 15cm.
3. 3

   Step 3: Add the three side lengths together to find the perimeter.

4. 4

   Step 4: Remember to include the units in your final answer.

Detailed Guide

About the Author