Depth of water when a conical tank is half full

A conical tank stands with its vertex pointing down. It has height \(60\) cm and top radius \(20\) cm. Water in the tank has depth \(h\) cm.

1. Show that the volume of water is \(\dfrac{\pi h^3}{27}\text{ cm}^3\).[3]
2. Find the depth of water when the tank is half full by volume.[2]
3. Explain why, when the tank is half full by volume, the depth is more than half the height of the tank.[2]