If 10 persons can do a job in 20 days than 20 persons with twice efficiency can do the same job in ____?

If 10 persons can do a job in 20 days than 20 persons with twice efficiency can do the same job in ____?

Explanation

10 persons can do the job in 20 days, which means the total work required is 10 x 20 = 200 person-days.

If 20 persons are working with twice the efficiency, their effective work capacity is doubled, so they can do the work of 40 persons (20 x 2).

Now, let's calculate the time taken by 20 persons with twice the efficiency to complete the same job:

Total work required = 200 person-days

Effective work capacity = 40 persons

Time taken = Total work required / Effective work capacity

= 200 person-days / 40 persons

= 5 days