Perimeter of a Triangle for Class 1

The reading material provided on this page for Formula for Perimeter of a Triangle is specifically designed for students in grades 5 and 6.

What is a Triangle?

Triangle is a closed figure made up of three-line segments. These line segments are said to be sides.

a) It has three sides.
b) It has three angles.
c) It has three vertices.

Types of Triangle

There are three types of triangles on the basis of sides.

a) Equilateral triangle
b) Isosceles triangle
c) Scalene triangle

Perimeter of a Triangle

The perimeter of a triangle is the total length of all its sides added together. It is a measure of the length around the outside of the triangle. A triangle have three sides, and the perimeter is calculated by adding all three sides together. The the unit of Perimeter of triangle depends on the unit of its sides in can be in cm, m, inches, feet etc.

Formula of Perimeter of a Triangle

The formula for the perimeter of a triangle is P = a + b + c,
where a, b and c are the lengths of the sides of the triangle.

Perimeter of an Equilateral Triangle

The perimeter of an equilateral triangle is the sum of the lengths of all its sides. An equilateral triangle has all its sides equal in length, so the perimeter is simply three times the length of one side.

Example: Let's consider an equilateral triangle with a side length of 5 units.

Solution: The perimeter of this triangle would be:
Perimeter = 3 x side
= 3 x 5
= 15 units.

So, the perimeter of this equilateral triangle is 15 units.

Perimeter of an Isosceles Triangle

The perimeter of an isosceles triangle is the total length of all three sides of the triangle. An isosceles triangle is a triangle that has two sides of equal length and the third side is slightly longer or shorter.

Example: Consider an isosceles triangle with two sides of length 10 units and third side 7 units. To find the perimeter, we add up the length of all three sides:
(2 x 10) + 7 = 27 units

Therefore, the perimeter of this isosceles triangle is 27 units.

Perimeter of a Scalene Triangle

A scalene triangle is a triangle where all three sides are of different lengths. The perimeter of a scalene triangle is simply the sum of the lengths of all three sides. So, if a scalene triangle has side lengths a, b and c, then its perimeter P can be calculated using the formula:

Example: If a scalene triangle has side lengths of 3 cm, 4 cm and 5 cm, then its perimeter is:

P = 3 cm + 4 cm + 5 cm = 12 cm