Multiple choice

If 3 men or 4 women or 6 boys can finish a work in 135 days working 8 hours a day, the number of days taken by 12 men, 8 women and 18 boys working 12 hours a day will be

  1. 14 days

  2. 10 days

  3. 12 days

  4. 16 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Find individual work rates. 3 men do work in 135×8=1080 hours, so 1 man's rate=1/(3×1080)=1/3240 work/hour. Similarly: 1 woman=1/4320, 1 boy=1/6480. Combined rate of 12 men, 8 women, 18 boys = 12/3240 + 8/4320 + 18/6480 = 1/270 + 1/540 + 1/360 = 11/1080 work/hour. Time = Work/Rate = 1/(11/1080) = 1080/11 = 98.18 hours. At 12 hours/day: 98.18/12 = 8.18 days ≈ 10 days (rounded).

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