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Three pipes of same capacity can fill a tank in 8 hours. If there are only two pipes of same capacity, the tank can be filled in___________?

Correct answer: B. 12 hours

  • A. 17 hours
  • B. 12 hours
  • C. 16 hours
  • D. 24 hours

Explanation

Three equal pipes fill 1 tank in 8 hours, so their combined rate is 1/8 tank/hour. Two of the identical pipes provide 2/3 of that rate, namely 1/12 tank/hour, and therefore take 12 hours. The likely mistake is choosing 16 hours by doubling the 8-hour time instead of adjusting the rate from three pipes to two.

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About Time and Work

Problems measure work through rates, treating each person's or machine's contribution as work completed per unit time. Questions cover combined work, efficiency, wages, alternate working schedules, pipes and cisterns, and men-days relationships, with care needed to distinguish time taken by one worker from the time required when workers act together.

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