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Question 909513: An inlet pipe on a swimming pool can be used to fill the pool in 25 hours. the drain pipe can be used to empty the pool in 30 hours. if the pool is 1/3 filled and then the inlet pipe and drain pipe are opened, how long from that time will it take to fill the pool.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! An inlet pipe on a swimming pool can be used to fill the pool in 25 hours. the drain pipe can be used to empty the pool in 30 hours. if the pool is 1/3 filled and then the inlet pipe and drain pipe are opened, how long from that time will it take to fill the pool.
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Fill Rate:: 1/25 job/hr
Empty Rate:: 1/30 job/hr
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Combined Rate:: (1/25)-(1/30) = 5/(25*30) = 1/(5*30) = 1/150 job/hr
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Equation:
rate*time = work done
(1/150)x = 2/3 job
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x = 100 hrs (time to fill (2/3) of the pool.
Cheers,
Stan H.
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