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If 28 men can finish a work in 15 days, 21 men can finish the same work in___________?

Correct answer: D. 20 days

  • A. 24 days
  • B. 14 days
  • C. 15 days
  • D. 20 days

Explanation

The total work is 28 men x 15 days = 420 man-days. Therefore, 21 men need 420 man-days ÷ 21 men = 20 days. Students may choose 24 days by using an incorrect inverse proportion calculation.

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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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