Two pipes S and T can fill a tank in 3 hours and 6 hours respectively. Pipe U can alone empty the same tank in 4 hours. If all three pipes are opened together, then in how many hours will the tank be filled?
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Two pipes S and T can fill a tank in 3 hours and 6 hours respectively. Pipe U can alone empty the same tank in 4 hours. If all three pipes are opened together, then in how many hours will the tank be filled?