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What You Need To Know About:
Calculating the Area of Circles - Online Calculator
Measuring Circles

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All about Circles - Tutorial

The distance all around a circle is called the Circumference and is referred to in formulas as C. The distance from one side of the circle to the other is referred to as the Diameter of a circle and is identified as a d in formulas. The Radius of a circle is the distance from the center of the circle to the outside edge. Thus the diameter of the circle is twice the size of the radius of a circle. The Area of a circle refers to the number of square units within the circle.

If you know the area, diameter or the circumference, you will be able to use this tool to determine the missing values. Some formulas worth know are:

Circumference = Pi (3.14) times Diameter (C=pD)

Diameter = 2 times the Radius (D=2R)

Area = Pi times the radius squared (A=pr2)
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