Method #1 – Radius from the Area
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Formula – How to calculate the radius of a semicircle from the area
π is approximately equal to 3.1415926535
Radius = √(2 x Area ÷ π)
Example
A semicircle has an area of 300
Radius = √(2 x 300 ÷ π)
Radius = √(2 x 300 ÷ 3.14159)
Radius = √190.986
Radius = 13.8198
Method #2 – Radius from the Circumference
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Formula – How to calculate the radius of a semicircle from the circumference
π is approximately equal to 3.1415926535
Radius = Circumference ÷ π
Example
A semicircle has a circumference of 35
Radius = 35 ÷ π = 35 ÷ 3.14159 = 11.14086
Method #3 – Radius from the Diameter
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Formula – How to calculate the radius of a semicircle from the diameter
Radius = Diameter ÷ 2
Example
A semicircle has a diameter of 20
Radius = 20 ÷ 2 = 10