Explanation:

Correct Option is : 1

Solution

Given:
Each man takes 20 days to complete the work
Calculation:
Let the efficiency of each man be 1
So, total work is 20 unit
So, on 1st day total work = 1 unit
Next day = 1 + 1 = 2 units
So according to this after 5th day total work has completed by 5 men = 1+2+3+4+5
⇒ 15 unit
So, remaining 20-15
⇒ 5 unit
It will be completed in 5/5 = 1 day
So total time taken by them to complete the work is = 5 + 1 = 6 days
- In 6 days, the work will be completed.