apparently they gave you the dimensions of the box, unless i am misinterpreting what that "4 cm x 4 cm x 12 cm" means.

in that case, we have

V = 16h

that's it. so h = V/16

now differentiate both sides with respect to time and plug in dV/dt

the reservoir is the cone?#2 A cone is filled with water at a rate of 6m^3/min.

If the reservoir is 3 m deep, and has a 4 m radius at the top, what is the rate at which the surface level of the water is rising at the instant the depth of the water is 2 m?

My answer:dh/dt = 16/6pi.

Are these answers right?

that's not the answer i got. what equation did you use?