Cylindrical tank rate of change

Water is pouring into a cylinder with a radius of 5m and height of 20m at a rate of 3 cubic metres a minute. Find the rate of change of height when the tank is half full.

Now the Volume V = $\pi {r}^{2}h$ and I can determine the rate of change in Volume is $dV/dt=\pi {r}^{2}dh/dt$ and the rate of change of height is $dh/dt=1/\pi {r}^{2}\times dV/dt$

Using that formula I can determine that the water is rising at a rate of $3/25\pi $ m/min. But I cannot seem to figure out how to factor in height so that it is half full. Or is this wrong?

Water is pouring into a cylinder with a radius of 5m and height of 20m at a rate of 3 cubic metres a minute. Find the rate of change of height when the tank is half full.

Now the Volume V = $\pi {r}^{2}h$ and I can determine the rate of change in Volume is $dV/dt=\pi {r}^{2}dh/dt$ and the rate of change of height is $dh/dt=1/\pi {r}^{2}\times dV/dt$

Using that formula I can determine that the water is rising at a rate of $3/25\pi $ m/min. But I cannot seem to figure out how to factor in height so that it is half full. Or is this wrong?