Question 33158
The basics of the problem are that you are finding the volume of water in a pool which is a cyllinder shape.  The formula for volume is V= (r^2)(h)(pi). Notice the formula requires the radius but we are given diamter so cut the diameter in half to get radius- half of 30 is 15.

Substituting what we know and simplifying:
22,000 gal = (15ft^2)(H)(pi)
(22,000gal)/(255 ft^2)(pi) = (H) H is in ft.
31.1236gal/sq.ft = H ft
Using 1cubic foot per 7.5 gal of water, we divide 31.1236 gal/7.5 giving you H=4.1498