Geometry

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.

perimeter of a triangle

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.

Result :

Worksheet 1

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Cheat sheet

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