Jonathan can type a 20 pages document in 40 minutes, susan can type it in 30 minutes. Jack can type it in 24 minutes. Working together, how much time will it take them to type same document?

Jonathan's rate = 20/40 = 1/2 page per minute

Susan's rate = 20/30 = 2/3 page per minute

Jack's rate = 20/24 = 5/6 page per minute

Combined rate for the three = 1/2 + 2/3 + 5/6 = 2 pages per minute

Therefore, working together, the will type the document in 20/2 = 10 minutes.