Question

how is dv/dt of a cylinder related to dh/dt when r is constant

Answer 1

we know that the volume of a cylinder, say v, is (pi)(r^2)h
to know teh relation between dv/dt and dh/dt when r is constant differentiate the above formula with respect to t keeping r constant

Answer 2

that would give you dv/dt=(pi)(r^2)(dh/dt)