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 day persons continued working as a team. In how many days, will the work be completed?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is Option 1. i.e 6.
Suppose 1 man does 1 unit of work in 1 day.
Total work = 1 × 20 = 20 units.
Work done on the very first day = 1 unit
Now one person with the same efficiency joins the team, so the work done on the second day = 2 units.
Similarly for the third day = 3 units.
Work done on the fifth day = 5 units.
Total work done in % days altogether = 1 + 2 + 3 + 4 + 5 = 15 units.
Work done on the sixth day = 15 + 5 = 20 units
Hence required number of days = 5 + 1 = 6 days