SOLUTION: When a bathtub faucet is turned on (and the drain is shut), it can fill a tub in 6 minutes; when the drain is open, a full bathtub can empty in 11 minutes. How long would it take f
Question 31642: When a bathtub faucet is turned on (and the drain is shut), it can fill a tub in 6 minutes; when the drain is open, a full bathtub can empty in 11 minutes. How long would it take for the bathtub to fill if the water were turned on with the drain left open? Answer by mbarugel(146) (Show Source):
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If the tub can be filled in 6 minutes with the faucet turned on, then the faucet fills 1/6 of the tub per minute.
Similarly, if a full tub can be emptied in 11 minutes when the drain is open, then the drain "fills" -1/11 of the tub per minute (filling a negative amount would be equivalent to draining it)
Therefore, when they are both working, they can fill:
of the tub per minute.
Based on this, we condlude that it will take 66/5 = 13.2 minutes to fill an empty tub when the faucet is turned on and the drain is open.