2002 · Q54
15 men can complete a work in 280 days. They started the work and after every 10 days, 15 additional men were employed. In how many days the work was completed?
General Mental Ability, Quantitative Aptitude and StatisticsTime, work and measurement
- A70 days
- B60 days
- C55 days
- D50 days
Explanation
Total work = 15 men × 280 days = 4200 man-days. Adding 15 men every 10 days, the work done in k ten-day blocks is 10×15×(1+2+…+k) = 75k(k+1) man-days. Setting 75k(k+1) ≥ 4200 gives k(k+1) ≥ 56, satisfied exactly at k = 7 — i.e. 70 days. Hence (A) is correct.