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How to Find the Perimeter of the Semicircular Region

A semicircle is the same as a half-circle. When calculating the perimeter of a semicircle, you need to know the diameter, which is the distance across the circle, passing through the center. With a semicircle, the diameter is the same as the flat side of the semicircle. You might need to find the perimeter of a semicircular region if you want to fence in the area.

Ruler

Instructions

- 1
  Measure the length of the straight line portion of the semicircle to find the diameter of the circle.
- 2
  Multiply the diameter by 3.14 to find the perimeter of the shape if it were a full circle. For example, if your diameter equals 11 inches, multiply 11 by 3.14 to get 34.54 inches.
- 3
  Divide the perimeter of the full circle by 2 to find the perimeter of the circular section of the semicircle. In this example, divide 34.54 inches by 2 to get 17.27 inches.
- 4
  Add the diameter to find the perimeter of the semicircular region. Completing the example, add 11 to 17.27 to find the perimeter equals 28.27 inches.

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