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How to Find a Circle's Diameter From Its Perimeter

Mathematicians define perimeter as the distance around a closed figure. The distance around a circle has the special name "circumference," although perimeter also describes this measurement. When you wish to find a circle's diameter from its perimeter (or circumference), you must first learn the special rule of ratio between the circumference and diameter of a circle. Armed with this understanding, the formula becomes simple.

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Instructions

- 1
  Understand the ratio of circle dimensions. The value "pi" (3.14) is the ratio of the circumference and the diameter.
- 2
  Write the equation you will perform. Since pi is equal to the circumference divided by the diameter, the equation is 3.14 (pi) = circumference/diameter.
- 3
  Perform the function to solve the equation and find the diameter. For example, if the perimeter (circumference) is 8.5 inches, divide 8.5 by 3.14 to get 2.7 inches. This means that the circle has a diameter of 2.7 inches.

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