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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