SOLUTION: An inlet pipe can fill a tank in 6 minutes. A drain can empty the tank in 8 minutes. If the tank is empty and both the pipe and drain are open, how long will it take before the tan

Question 134620: An inlet pipe can fill a tank in 6 minutes. A drain can empty the tank in 8 minutes. If the tank is empty and both the pipe and drain are open, how long will it take before the tank over flows?
Found 2 solutions by solver91311, vleith:
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!
The inlet can fill the tank in 6 minutes, so it fills of the tank in 1 minute. Likewise the drain can empty the take at a rate of tank per minute.

Filling and draining at the same time, the tank will fill at a rate of . So of the tank fills per minute, and the fluid will reach the top of the tank in 24 minutes.
Answer by vleith(2983) (Show Source): You can put this solution on YOUR website!
Think about what happens in the time it takes to 'fill the tank'. With the drain open, 6/8th of the water will drain in the time it would take to fill the tank with the drain closed.
So instead of having a full tank, we have a a tank that is (1 - 3/4) full = 1/4 full.
So the tank fills 1/4 of the way every 6 minutes.
How many minutes to fill it at that rate?? We will need to add in 1/4 + 1/4 + 1/4 + 1/4 = 1
We need 4 times the 6 minutes to fill the tank. ==> 24 minutes

Look at it another way, You could fill the tank 4 times in 24 minutes if the drain was closed. You could drain the tank 3 times in 24 minutes if you had 3 full tanks ready to rock and roll.
Net 4 - 3 = 1 tank after 24 minutes.

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