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# Perimeter of a Triangle

## The Perimeter Formula

A triangle is a polygon with three sides and three vertices. The formula for perimeter is given as:**P = a + b + c**

Where *P* is the perimeter, and *a* *b* and *c* are the three side lengths.

### Example Problems

**Problem 1:**

What is the perimeter of a triangle with side lengths of 5, 6, and 3?

Solution:

Let’s plug the side lengths into the perimeter formula.

P = a + b + c

P = 5 + 6 + 3 = 14**The perimeter of the triangle is 14.**

**Problem 2:**

An equilateral triangle has a perimeter measured to be 81 centimeters. What are the side lengths?

Solution:

Since an equilateral triangle has three equal sides, a = b = c. We can substitute a + b + c with 3a.

Plugging what we know into the perimeter formula, we get:

P = a + b + c

81 = 3a

a = 27, b = 27, c = 27**The three sides each have a length of 27 centimeters.**