What is Perimeter?
Perimeter is the total length of the boundary of a closed shape. It is found by adding up the lengths of all the sides of the shape. In simple terms, if you walk around the edge of a shape and measure the distance you covered, that distance is the perimeter.
1. Perimeter of a Circle (Circumference)
• The perimeter of a circle is called its circumference.
• Formula:
C = 2πr
or
C = πd
where:
• C = circumference
• r = radius of the circle
• d = diameter of the circle
2. Perimeter of a Square
• A square has four equal sides.
• Formula:
P = 4s
where:
• P = perimeter
• s = length of one side
3. Perimeter of a Rectangle
• A rectangle has two pairs of equal opposite sides.
• Formula:
P = 2(l + w)
where:
• P = perimeter
• l = length
• w = width
4. Perimeter of a Triangle
• The perimeter of a triangle is the sum of its three sides.
• Formula:
P = a + b + c
where:
• P = perimeter
• a,b,c = lengths of the three sides
For an equilateral triangle (all sides equal):
P = 3s
where s is the length of one side.
For a right-angled triangle, if two sides are given, the third side can be found
using the Pythagorean theorem before calculating the perimeter:
c2 = a2 + b2