20 men can construct a building in 40 days. How long will it take 10 men to do this work?

20 men can construct a building in 40 days. How long will it take 10 men to do this work?

Explanation

20 men can construct a building in 40 days.

Total work = 20 men × 40 days = 800 man-days.

Time = Total work / Number of men = 800 man-days / 10 men = 80 days.