If 3 persons do 3 times of a particular work in 3 days, then 7 persons can do 7 times of that work in _________.

If 3 persons do 3 times of a particular work in 3 days, then 7 persons can do 7 times of that work in _________.

Explanation

3 persons can do 3 jobs in 3 days

1/3 of the work will take 1/3 of the time, so

3 people can do 1 job in 1 day

It will take 1 person 3 times as long, so

1 person can do 1 job in 3 days

7 persons can do 7 times the work in the same time, so

7 persons can do 7 jobs in 3 days