Work backwards to find the radius, then find the diameter
FIND RADIUS
Area= πr^2
Plug in the numbers you know
64π= πr^2
divide both sides with π from the RIGHT side of the equation
64π/π= r^2
π/π= 1 so it "cancels out"
64= r^2
√64= √r^2
take the square root of 64 to find r (what # times itself equals 64)
8 inches= r
FIND DIAMETER
diameter= radius * 2
diameter= 8 * 2
diameter= 16 in^2
ANSWER: The diameter is 16 in^2
Hope this helps! :)