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How to Find the Perimeter of a Circle by Using the Area

The circle perimeter is the length around the circle commonly referred to as a circumference. Circumference calculations are a common math assignment. To compute this value, you need the circle radius or diameter. The area of the circle measured in square units, such as square inches, is given by the formula: constant "pi" x Radius x Radius. This expression allows you to calculate the required radius value.

Things You'll Need

Calculator

Instructions

- 1
  Divide the area of the circle by the constant "pi" (3.142). For example, if the area is 40 square inches then 40/3.142 = 12.73.
- 2
  Take the square root of the result of the division to compute the radius of the circle. In this example, the radius is square root (12.73) = 3.57 inches.
- 3
  Multiply the radius of the circle by two to calculate the diameter. In this example, the circle diameter is 3.57 x 2 = 7.14 inches.
- 4
  Multiply the diameter of the circle by the constant "pi" (3.142) to calculate the circle circumference (perimeter). In this example, the perimeter is 7.14 x 3.142 = 22.43 inches.

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