Multiple choice

Fifteen men could finish a piece of work in 210 days. But at the end of every 10 days, 15 additional men are employed. In how many days will the work be finished?

  1. 60 days

  2. 70 days

  3. 90 days

  4. 100 days
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Total work = 15 * 210 = 3150 man-days. Days 1-10: 15 men * 10 days = 150. Days 11-20: 30 men * 10 days = 300. Days 21-30: 45 men * 10 days = 450. Days 31-40: 60 men * 10 days = 600. Days 41-50: 75 men * 10 days = 750. Days 51-60: 90 men * 10 days = 900. Sum = 150+300+450+600+750+900 = 3150. Work finished in 60 days.

AI explanation

The total work is 15 men multiplied by 210 days, equaling 3150 man-days. In each 10-day cycle, the men employed are 15, then 30, then 45, then 60, then 75, completing 2250 man-days of work in 50 days. This leaves 900 man-days of work, and since the next cycle brings in 90 men, they will do 900 man-days of work in exactly 10 days. The total time is 50 plus 10 days. The result is 60 days.

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