I know the answer to the problem (5.508), but I'm not sure how to do it myself for a test or something. If someone could do it out so I can learn how to do it, because I have bout 6 more of these to do on my own. Thank you.

Grain is falling from a chute onto the ground, forming a conical pile whose diameter is always 4 times its height. How high is the pile to the nearest hundredth of a foot when it contains 700ft3 of grain?

Height of the pile =?