Posted by Jen on Friday, July 29, 2011 at 11:19pm.
What is the exact circumference of a circle with a diameter of 21 inches?
Is it 110.25p inches??

Math  Bosnian, Saturday, July 30, 2011 at 1:57am
In google type:
circumference of a circle
When you see list of results go on wikipedia.
C = circumference
d = diameter
C = d*pi
C = 21*3.14159
C = 65.97339 in

Math  Reiny, Saturday, July 30, 2011 at 7:38am
Circumference = 2πr or dπ with d as diameter
so circumference = 21π
(it asked for "exact" circumference , so the answer has to be left in terms of π )
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