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A certain water tank has two outlet valves, valve \(A\) and valve \(B.\) Each valve drains water from the tank at a constant rate. If the tank is full and valve \(B\) alone is opened, does it take more than two hours to completely drain the tank?
(1) When the tank is full, if valve \(A\) alone is opened, it takes \(4\) hours to completely drain the tank.
(2) When the tank is full, if valve \(A\) is opened and valve \(B\) is opened an hour later, it takes \(\dfrac43\) as long to completely drain the tank as it would if both valves had been opened simultaneously from the start.
Answer: B
Source: Princeton Review
(1) When the tank is full, if valve \(A\) alone is opened, it takes \(4\) hours to completely drain the tank.
(2) When the tank is full, if valve \(A\) is opened and valve \(B\) is opened an hour later, it takes \(\dfrac43\) as long to completely drain the tank as it would if both valves had been opened simultaneously from the start.
Answer: B
Source: Princeton Review
