<PRE><B>Question 154584</B>
an inlet pipe can fill a tank in 1 hour, a drain pipe can empty it in 3/2 hours. The inlet pipe was opened at 6:00 a.m. to fill the tank. At 6:20a.m. someone noticed that the drain has been left open and so he closes it immediately. How long will it take the first pipe to finish filling
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Filling pipe rate = 1 job/hour
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Draining pipe rate = 3/2 job/hour
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Together rate: 1-3/2 = -(1/2) job/hour
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EQUATION:
Both were operating  from 6:00am till 6:20am or 1/3 hour.
In that time the tank would stay empty because the drain
pipe is removing water as fast as the inlet pipe puts it 
in.
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The inlet pipe will then take 1 hour to fill the tank.
It should be full at 7:20 am.
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Cheers,
Stan H.

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