Area of a Circle

Area of a Circle

How to find the area of a circle: formula, examples, and their solutions.

Formula

A = pi*r^2, A: Area of a circle, pi: 3.141592..., r: Radius of a circle

A = πr2

A: Area of a circle
π = 3.141592...
r: Radius of a circle

Example 1

Find the area of the given circle. r = 5.

r = 5

So A = π⋅52.

52 = 25

So A = 25π.

Example 2

Find the area of the given circle. d = 13.

d = 13

So r = 13/2.

Then A = π⋅(13/2)2.

(13/2)2 = 132/22

Power of a quotient

132 = 169
22 = 4

So A = (169/4)π.