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| Math Central | Quandaries & Queries |
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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,
Penny
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