Math
posted by Jen on .
What is the exact circumference of a circle with a diameter of 21 inches?
Is it 110.25p inches??

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 
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 )