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| Question 513102:  A pipe can fill a pool by itself in 2 hours. Another pipe can drain a pool filled with water in 3 hours. If 3 pipes of the first kind bring in water to the pool, while 4 pipes drain water, simultaneously, after how many hours will the pool be filled?
 Answer by Alan3354(69443)
      (Show Source): 
You can put this solution on YOUR website! A pipe can fill a pool by itself in 2 hours. Another pipe can drain a pool filled with water in 3 hours. If 3 pipes of the first kind bring in water to the pool, while 4 pipes drain water, simultaneously, after how many hours will the pool be filled? -----------------------
 A pipe can fill a pool by itself in 2 hours.
 3 of these can fill the pool in 2/3 hours, or can fill 1.5 pools per hour.
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 Another pipe can drain a pool filled with water in 3 hours.
 4 of these can drain the pool in 3/4 hour, can drain 4/3 pools per hour.
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 3/2 filled - 4/3 emptied per hour = 1/6 pool per hour
 --> 6 hours per pool
 
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