Each one of five men independently can complete a work in 20 days. The work is started by one person. Next day one more person joins and every next day one more person joins. From the fifth day, five persons continued working as a team. In how many days, will the work be completed?

6

Each Man takes 20 days to complete the work.

Let the efficiency of each man be 1.

Given,

Day 1 = 1 

Day 2 = 1 + 1 = 2

Day 3 = 1 + 1 + 1 = 3

Day 4 = 1 + 1 + 1 + 1 = 4

Day 5 = 1 + 1 + 1 + 1 + 1 = 5

5 days = 15 units of work 

Remaining work = 5 units. 

Time taken by all of the to complete 5 units = \(\frac{5}{5}\) = 1 day.

Therefore, work will be completed in 5 + 1 = 6 days.