What is the circumference of a circle when the area is 36 pi?

To convert area into circumference, take the two formulas for circles--circumference and area:

C=2pi*r

A=pi*r^2

Now, isolate the common variable (r) in the second equation.

r=sqrt(A/pi)

Now you can substitute this in for "r" in the first equation to find circumference

C=2pi*sqrt(A/pi)

C=2pi*sqrt(36pi/pi) pi cancels out

C=2pi*sqrt(36)

C=2pi*6

C=12pi