Multiple choice

A certain number of men can do a work in 60 days. If there were 15 men more it could be finished in 10 days less. How many men were there in the beginning ?

  1. 60

  2. 70

  3. 75

  4. 80
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let M = initial men, work = M × 60 man-days. With M + 15 men: (M + 15) × 50 = M × 60. Solve: 50M + 750 = 60M → 750 = 10M → M = 75. Verification: 75 men can do work in 60 days. 90 men (75 + 15) would take 75 × 60 / 90 = 50 days, which is 10 days less.

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