# Area of Circle

The area of a circle is the region occupied by the circle in a two-dimensional plane. It can be determined easily using a formula, A = πr2(Pi r-squared) where r is the radius of the circle. The unit of area is the square unit, such as m2, cm2, etc.

### Calculation of Area of Circle

For example, if the radius of circle is 7cm, then its area will be:
Area of circle with 7 cm radius = πr2 = π(7)2 = 22/7 x 7 x 7 = 22 x 7 = 154 sq.cm.

Also, if we know the circumference of the circle, then we can find the area of a circle.
How?
Since, the circumference is 2 times of product of pi and the radius of the circle, such as:
C = 2πr
Therefore, here we can find the value of the radius,
r = C/2π
Once, we have evaluated the value of the radius, we can easily find the area.

### What is the area of this circle?

 Area = π × r2 = π × 32 = π × (3 × 3) = 3.14159… × 9 = 28.27 (to 2 decimal places)

## How to Calculate the Area

The area of a circle is:

π (Pi) times the Radius squared: A = π r2
or, when you know the Diameter: A = (π/4) × D2
or, when you know the Circumference: A = C2 / 4π

#### Radius Of A Circle And Chord

The radius of a circle is the distance from the center of the circle to any point on its circumference. It is usually denoted by ‘R’ or ‘r’. This quantity has importance in almost all circle-related formulas.

Concerning area and circumference, we can write the formula for the radius as:

 R = C/2π And R =  √(A/π) Also, R = D/2

Solved Examples

Let us see some solved problems on the radius and chord of a circle.

Example 1: Find the radius of the circle if its diameter is 16 cm.

Solution:

Given,

Diameter of circle = 16 cm