text: Man-hour required to do the job = 10*12 = 120\nMan-hour required to do 1/4 0f the job = 120/4 = 30\nNumber of hours required to do 1/4 of the job by 6 people = 30/6 = 5 hrs.\n\nI find this method of using man-hour useful.. You can also use a method called "unitary method".