If 10 persons can do a job in 20 days, then 20 persons with twice the efficiency can do the same job in -

Question: If 10 persons can do a job in 20 days, then 20 persons with twice the efficiency can do the same job in -

Solution:
10 persons in one day can do = 1/20
20 persons in one day can do = 2 × 1/20 = 1/10

with double efficiency, in one day they can do = 2 × 1/10 = 1/5

so, the work will be finished in just 5 days