Question

A conical tank (with its tip down and the circular base parallel to and above the ground) is filling with water in such a way that the height of the water is increasing at a rate of 0.1cm/hr at the instant that the height of the water level is 10cm. If the tank has a radius of 12cm and a height of 30cm, find how fast the area corresponding to the top of the water level is increasing at this instant.