Area of Circles. Finding The Area of a Circle Using Pi

How to find the area of a circle using A = π × r²

To find the area of circle you multiply Pi by the square of the radius. The radius is the distance half way across the centre of the circle, and Pi is a mathematical constant equal to 3.14 (to 2 decimal places). If you have a scientific calculator then use the Pi button (π).

This can be written as a formula:

A = π × r²

A is the area, π is Pi and r is the radius of the circle.

Let’s take a look at a couple of questions. Make sure that you use the radius in your calculations.

Question 1

Find the area of this circle.

A = π × r²

A = π × 6²             (substitute 6 into your formula, as 6 is the radius)

A= 113.1 cm² to 1 decimal place.

Question 2

Find the area of this circle.

This time you are given the diameter of the circle, so we need to half this answer to give you the radius.

So ½ of 58 = 29 cm

Now use your formula to find the area:

A = π × r²

A = π × 29²           (substitute 6 into your formula, as 6 is the radius)

A= 2642.1 cm² to 1 decimal place.

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