well, the area of a circle = [tex] \pi [/tex][tex] r^{2} [/tex]
so 36 pi = r^2 pi
the pi's cancel and you're left with 36 = r^2
square root both sides to get [tex] \sqrt{36} [/tex] = r
and r = + or - 6
However, a circle cannot have a negative radius so r = 6 and only a circle with a radius of 6 has an area of 36 pi
To answer your question briefly, there is one circle with an area of 36 pi
