12 men working 5 hours a day can do a piece of work in 36 days. In how many days can 10 men working 9 hours a day do the same work?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 24
For the same work, the total man-hours stay the same: men \(\times\) hours per day \(\times\) days is fixed.
Man-hours needed \(=12\times5\times36=2160\)
Man-hours in one day with 10 men working 9 hours \(=10\times9=90\)
Days needed \(\displaystyle =\frac{2160}{90}=24\)
10 men working 9 hours a day finish the work in 24 days.