# Circle: Area

How to find the area of a circle: formula, 2 examples, and their solutions.

## Formula

A = πr^{2}

A: Area of a circle

r: Radius

## Exampler = 5, A = ?

Solution

Solution (Detail)

r = 5

A = π⋅5^{2}

5^{2} = 25

So π⋅5^{2} = 25π.

So the area of the given circle is 25π.

## ExampleDiameter: 13, A = ?

Solution

Solution (Detail)

The diameter is 13.

So the radius is the half of the diameter:

13/2.

r = 13/2

A = π⋅[13/2]^{2}

[13/2]^{2} = 13^{2}/2^{2}

Power of a Quotient

So π⋅[13/2]^{2} = [13^{2}/2^{2}]π.

13^{2} = 169

2^{2} = 4

So [13^{2}/2^{2}]π = [169/4]π.

So [169/4]π is the answer.