Five drainage pipes, each draining water from a pool at the same constant rate, together can drain a certain pool in 8 days. How many additional pipes, each draining water at the same constant rate, will be needed to drain the pool in 4 days?
Choose one
A) 5  B) 9  C) 10  D) 12  E) 15
This is an inverse proportional problem......   5 pipes in 8 days; So for 4 days, it will be = 8 x 5 / 4 = 10   So, 10-5 = 5   5nswer 5
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Five drainage pipes, each draining water from a pool at the same constant rate, together can drain a certain pool in 8 days. How many additional pipes, each draining water at the same constant rate, will be needed to drain the pool in 4 days?