60 men can complete a work in 40 days. They start work together but after every 10 day, 5 men leave the work. In how many days will the work be completed?

47.5

60 men can complete work in 40 days; 

⇒ Assume efficiency of men as 1,

⇒ Total work = 60(1) x 40 = 2400 units.

According to the question, every 10 days 5 men left.

⇒ (60 x 10) + (55 x 10) + (50 x 10) + (45 x 10) = 2100 units

⇒Remaining work = 2400 -2100 = 300 units. 

⇒ Now 40 men will complete 300 units of work = \(\frac{300}{40}\) = 7.5

⇒ Total no. of days to finish the work = 40 + 7.5 = 47.5 days.

Therefore, the work will be completed in 47.5 days.