A geometry/derivative word problem
I know you suppose to find an equation and take the derivative, but how to do it i don't know.
a container has the shape of an open right circular cone, as shown in the figure above. The height of the container is 10 cm and the diameter of the opening is 10 cm. Water in the container is evaporating so that it depth h is changing at the constant rate of -3/10 cm/hr.
The volume of a cone of height h and radius r is given by V=1/3 pi r^2 h
a) Find the volume V of water in the container when h=5 cm.
b) find the rate of change of volume of water in the container, with respect to time, when h=5 cm.