Question 1131119
 "At noon, a pump is turned on to fill an empty pool. Normally, the pump would fill the pool in 12 hours, but at 12:00 P.M, a valve is accidentally opened that could drain a full pool in 20 hours. If the valve remains open, at what time will the pool be full?"
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1st pump data:
rate = 1/12 pool/hr
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2nd pump data:
rate = -1/20 pool/hr
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Rate at which the pool is filled if both are pumps are open:: 1/12 - 1/20
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Let the time to fill the pool be x-hours.
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x(1/12 - 1/20) = 1 pool
x((20-12)/(12*20)) = 1
x(8/240) = 1
x(1/30) = 1
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Ans:: Time to fill the pool = 30 hours.
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Cheers,
Stan H.
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