A pipe fills a tank in 4 hours. Another empties in 6. Net time?
Correct answer: C. 24 hours
- A. 10 hours
- B. 12 hours
- C. 24 hours
- D. 8 hours
Explanation
To determine the net time to fill the tank, calculate the rates of the pipes: the filling pipe fills the tank at a rate of 1/4 per hour, while the emptying pipe empties it at a rate of 1/6 per hour. The net rate is therefore 1/4 - 1/6 = 1/12 of the tank per hour. Thus, it takes 12 hours to fill 1/12 of the tank. For the complete tank, it would therefore take 12 × 2 = 24 hours. Options A, B, and D do not accurately account for the net rate of filling the tank.
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Logical problems present several conditions about people, objects, events or choices and require their possible arrangements to be tested. They cover constraint-based reasoning, rankings, matching, grouping, scheduling and elimination, with attention to the difference between a complete solution and a possibility that merely satisfies one condition.
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