Math CentralQuandaries & Queries


Question from Kathie, a student:

I know the length of the curved portion of a semi-circle is 200 ft. but I need to find the diameter to get a total perimeter and area. How do I find the diameter to get the perimeter?

Hi Kathie,

The circumference of a circle is π d where d is the diameter and π is approximately 3.1416. Since you have a semi-circle (half way around the circle) of length 200 ft the circle has circumference 2 × 200 = 400 ft. Thus

400 = π d

and hence

d = 400/π = 127.32 ft.

I hope this helps,

About Math Central


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences.
Quandaries & Queries page Home page University of Regina PIMS