Related Rates: Calculating Height and Radius of a Conical Pile

[Willowz]

Homework Statement

Sand falls from a conveyor belt at the rate of 10 m^3/min onto the top of a conical pile. The height of the pile is always three-eighths of the base diameter. How fast are the a) height and b) radius changing when the pile is 4m high?

Homework Equations

h = 3/8 * 2r

The Attempt at a Solution

I'm not sure where to start. I just need a small hint.

 

[Dick]

The question is giving you dV/dt. What's the equation for the volume of a cone in terms of r and h? That's a small hint.

 

[Willowz]

More than enough. Thanks

 

[cepheid]

The rate of change of the volume of the cone is 10 m³ per minute. What is the expression for the volume of a cone in terms of its height and base radius? This will allow you determine dr/t or dh/t in terms of dV/dt.

EDIT: two minutes too late...