



 
Hi Steve, I drew a cross section of the pool assuming that there is a constant slope from 4 ft to 9 ft deep. The volume of the pool is the area of this cross section time the width of 40 ft.
I drew a line on the diagram to divide it into a rectangle of length 50 ft and height 4 ft and a triangle with base 50 ft and height 9  4 = 5 ft. The area of the cross section is then the sum of the areas of the rectangle and the triangle. Penny  


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