A tank is half full. Pipe A can fill the whole tank in 16 hours and pipe B can empty it in 24 hours. If both are opened, in how many hours will the tank be full?
Correct answer D. 24 hours
Explanation
Net filling rate = 1/16 − 1/24 = 1/48 per hour. The remaining half takes 1/2 × 48 = 24 hours.
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