You can put this solution on YOUR website! How many 2.5 inch balls would it take to fill a pool 8 feet long by 5 feet wide and 2 feet high.
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Is 2.5 the diameter or the radius?
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You can find the volume of the pool = L*W*H.
Change the dim's to inches first.
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For a sphere,
Dividing the volume of the pool by the volume of a ball will give an approximation of the number of balls.
Stacking and packing can be complex.