Find the Area of a Circle

This activity is about finding the areas of circles.

You need to learn this important formula for a circle of radius, r :

Area of a circle = π r²

What is pi (π) in numbers?  Pi is an infinite number, and you can use a function on your calculator to input the number.

Here is the start of it  3.14159265359...

In this activity, you will need to use a scientific calculator to calculate the answers.  You can use one online if you do not have one in your home.

Example

Find the area of a circle of radius 6 cm.

Answer

Area = π r² =  π × 6² = π × 36 = 113.097335529 

We need to give our answer to 1 decimal place

This means that if the second number after the decimal point is 5 or higher, then we round the number straight after the decimal point up. If the second number after the decimal point is less than 5, we leave the number after the decimal point the same.

Area = π r² =  π × 6² = π × 36 = 113.1 cm²  

Remember, in this activity, you need to use a scientific calculator to calculate pi correctly, you can access one of these online.