Hi Jerri,

I drew a sketch of the pool and stone (not to scale).

The pool is 15 feet by 30 feet and the stone region is 4 feet wide all the way around so the external dimension of the pool and stone are $15 + 4 + 4 = 23$ feet by $30 + 4 + 4 = 38$ feet. You can find the volume you want by first finding the volume of a rectangular region which is 23 feet by 38 feet by 4 inches and then removing the volume of a region that is 15 feet by 30 feet by 4 inches. Both of these volumes you can calculate by using our volume calculator.

Write back if you need more assistance,
Penny