Which of the following describe this formula correctly: $S = 2\pi rh$
1.S is jointly proportional to radius and height
2.S is directly proportional to radius and height or
3.S varies directly with radius and height.
I am leaning towards choice 3 but I am not 100% positive.
This is stuff on variation that might help. k is a constant
"S varies as x" means S = kx "S varies jointly as x and y" means S = kxy "S varies as x + y" means S = k(x + y) "S varies inversely as x" means S = k/x