



 
Hi Ron, The volume of the pool is the area of the crosssection times the width of 20 feet. If the bottom of the pool is a gradual slope from 3 feet to 10 feet then the crosssection is a trapezoid. The area of a trapezoid is the average of the lengths of the parallel sides times the distance between the parallel sides. In this case the average of the length of the parallel sides is (10 + 3)/2 feet and the distance between the parallel sides is 40 feet. I hope this helps,  


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