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In this module, you can study what the area of a circle is and how to find the area of a circle if you know its diameter or radius.

The video above shows you how to calculate the area of a circle if you know either the radius or the diameter.

The above video shows a visual explanation of the area formula. In other words, it shows you WHY the area of a circle equals pi times radius squared.

If a circle and a square have the same perimeter, their areas will be different.

Pi times r-squared means Pi x radius x radius. It does NOT mean Pi x radius x 2.

- Try your hand at changing the area enclosed by a circleThis page on mathopenref.com lets you see how the area of the circle changes as you adjust its radius.
- Read about how to find the area of a circleThis link from mathisfun.com shows how to use different formulae to find the area of a circle. Also, there's a special calculator you can use that's just for finding the area of a circle.
- Quiz yourself on finding the area of circlesThis quiz at aaastudy.com will help you check your understanding of the circle area calculation.

Use these search terms to find additional resources:

*how to find the area of a circlecircle area*