How to Calculate the Area of a Circle



In this video we will learn how to calculate the area of a circle and how to find the area of a ring. Double-click the play button to start the video.



If you want to quickly find the area of a circle, use this free online geometry calculator.

Definitions

The distance around a circle is called the circumference.
The surface inside a circle is called the area of the circle.

A segment connecting the center of a circle with any point from the circle is called radius.

A segment that passes through the center of a circle and connects two opposite points from the circle is called diameter.

The radius is half the diameter.

Example

The radius of a large pizza is 20 inches. Find its area and round the answer to the nearest whole number.

First, we have to find the radius of the pizza.

r = d/2 = 20/2 = 10 in

Area = 3.14 x 10^2 = 3.14 x 100 = 314 square inches

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