Math CentralQuandaries & Queries


Question from Jerri:

I have a rectangular pool 15x30 and it will require stone placed around it 4 feet out and 4 inches deep how much will I need? Thanks, jerri

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,

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