SOLUTION: If it takes Tap A 4 hours to fill an empty tank and Tap B 6 hours to drain the same tank when full, how long will it take for the tank to fill up when both taps are open?

Question 997755: If it takes Tap A 4 hours to fill an empty tank and Tap B 6 hours to drain the same tank when full, how long will it take for the tank to fill up when both taps are open?
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
If it takes Tap A 4 hours to fill an empty tank and Tap B 6 hours to drain the same tank when full, how long will it take for the tank to fill up when both taps are open?
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Tap A adds 1/4 tank/hour
Tap B adds -1/6 tank/hour
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Together, 1/4 - 1/6 = 1/12 tank/hr
--> 12 hours/tank

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