<PRE><B>Question 270702</B>
An inlet pipe can fill a tank in 10 minutes.. A drain can empty the tank in 12 minutes. If the tank is empty and both the pipe and the drain are open, how long will it take before the tank overflows?
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Inlet rate: 1/10 job/min
Outlet rate: 1/12 job/min
Together rate: 1/x job/min
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Equation:
inrate - outrate = together rate
1/10 - 1/12 = 1/x
2/(120) = 1/x 
Invert:
x = 60 minutes
Time to fill the tank
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Cheer,
Stan H.</PRE>