Find Areas of Circles Using Their Radiuses

This worksheet is about finding the areas of circles.

You must 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 if the second number after the decimal point is 5 or higher then we round the number straight after the decimal point up one number, 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.