V o l u m = 4 3 ⋅ π ⋅ r 3
S u r f a c e A r e a = 4 ⋅ π ⋅ r 2
r = V ⋅ 3 4 ⋅ π 3
Or
r = S u r f a c e A r e a 4 ⋅ π
