first, note that

make a sketch of the conical tank.

get a proportional geometric relationship between the radius of the cone and the height ... solve for r in terms of h

derive the volume of water in the tank strictly in terms of the height

take the time derivative of your tank volume equation

sub in your given values and determine the value of dV/dt = volume in - volume leaking

... you're given dr/dt and r ... take the time derivative and find dV/dt2) The radius of a sphere is increasing at a rate of 4mm/sec. How fast is the volume increasing when the diameter is 80mm? how fast is the surface area increasing for the same diameter?

... same drill as above except find dA/dt