Question 206776
A water tank has an inlet pipe and a drain pipe. A full tank came be emptied in 30 minutes if the drain is opened and an empty tank can be filled in 45 minutes with the inlet pipe opened. If both pipes are accidently opened when the tank is full, then how long will it take to empty the tank?
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Water flows out at 1/30 of a tank per minute.
Water flows in at 1/45 of a tank per minute.
The diff is 1/30 - 1/45 = 1/90 tank per minute.
--> 90 minutes for the tank to empty.