Explanation

Given that 12 men can water the field in 9 hours, we can calculate the total man-hours required:

Total man-hours = 12 men * 9 hours = 108 man-hours

If the same field needs to be watered in 4 hours, let's denote the number of men required as x:

x men * 4 hours = 108 man-hours

x = 108 / 4

x = 27