# What is Perimeter of Triangle?

The perimeter of a triangle is defined as the total length of its boundary. A triangle is a polygon with 3 sides and it can be classified into different types based on the measure of its sides and angles. There are different formulas and methods to calculate the perimeter of a triangle based on the type of triangle.

Perimeter = Sum of the three sides

Always include units in the final answer. If the sides of the triangle are measured in centimeters, then the final answer should also be in centimeters.

### The Perimeter of Triangle Formula

The formula for the perimeter of a closed shape figure is usually equal to the length of the outer line of the figure. Therefore, in the case of a triangle, It will be the sum of all the three sides. If a triangle has three sides a, b and c, then,

P = a + b +c

#### Perimeter of Right Triangle

A right triangle has a base(b), hypotenuse(h) and perpendicular(p) as its sides, By the Pythagoras theorem, we know,

h2 = b2 + p2

Therefore, the Perimeter of a right angle triangle= b + p + h

• Ex 1: Calculate the Perimeter of a Right Triangle with a Base of 3 cm and a height of 4 cm.

First, using the Pythagorean theorem, calculate the hypotenuse of the right triangle.

hypotenuse =√(base2+perpendicular2)

h = √(32+42)

h = √(9 + 16)

hypotenuse = √25

Or, h = 5 cm

So, P = 3 + 4 + 5 = 12 cm.

• Example 2: Find the perimeter of a polygon whose sides are 5 cm, 4 cm and 2 cm.

Solution: Let,

a = 5 cm

b = 4 cm

c = 2 cm

P = Sum of all sides = a + b + c = 5 + 4 + 2 = 11

Therefore, the answer is 11 cm.

• Example 3: Find the perimeter of a triangle whose each side is 10 cm.

Solution: Since all three sides are equal in length, the triangle is equilateral.

i.e. a = b = c = 10 cm

P = a + b + c

= 10 + 10 + 10

= 30

P = 30 cm.