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A large tanker can be filled by two pipes A and B in 60 and 40 minutes respectively. How many minutes will it take to fill the tanker from empty state if B is used for half the time and A and B fill it together for the other half?

Correct answer: D. 30 min

  • A. 15 min
  • B. 20 min
  • C. 27.5 min
  • D. 30 min

Explanation

Let the total time be T minutes. B operates for T/2 at 1/40 tank per minute, and both pipes operate for T/2 at 1/24 tank per minute, so the filled fraction is T/2 x (1/40 + 1/24) = T/30. Equating this to 1 gives T = 30 minutes. The likely mistake is choosing 20 minutes by mishandling the two half-time intervals.

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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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