Three men can complete a job in 3 days, working 3 hours a day. In how many days can 9 men complete it working 1 hour a day?

3

The formula that we used here is :-

M1 × D1 × H1 = M2 × D2 × H2

Where, M = Number of men

D = Number of days

H = Number of Hours taken

ATQ,

M1 × D1 × H1 = M2 × D2 × H2

3 × 3 × 3 = 9 × D2 × 1

27 = 9 × D2 

D2 = 3

So, Number of time taken by 9 men to complete the same work is 3 days.