60 men can do a work in 40 days. how long will it take 40 men to complete the same work ?

A. 60 days
B. 30 days
C. 29 days
D. 23 days

If 60 men can finish work in 40 days then 40 men can finish the work in 60 days.

Men × days = men1 × days1

60 × 40 = 40 × x

x = 60 days