area equals pi r squared therefor r squared equals area over pi. Now find square root of r squared and you have "R" (radius) = 2.821
Square units
First divide the diameter by 2, to get the radius. Then use the formula area = pi x radius2.
Just 'cos! Square units are used for all areas; if you multiply m inches by n inches you get mn sq in
The area of a circle with a circumference of 37.68 units is: 113 square units.