Question

How many feet of monkey grass would you need to go around a circular flower bed if you know that the area is 36π ft2?

Answer 1

work out the perimeter 
36 pi = pi r^2
so r^2 = 36 and r = 6
perimeter = 2 pi r =  12 pi ft

Answer 2

A=pr^2 and C=2pr

Solving for r in area gives you:

r=√(A/p), and using this in the circumference equation gives you:

C=2p√(A/p)

C=√((4Ap^2)/(p))

C=√(4Ap) ft, now given that A=36p:

C=√(144p^2) ft

C=12p ft