There are 160 students transported by a bus that can carry 40 people 60 kilometers away from the school. A method of combining walking and cycling is designed to make them play their greatest role.

160 people were divided into four groups with 40 people in each group. The first group takes a bus to A and then walks, the second group takes a bus to C and then walks, the third group takes a bus to F and then walks, the fourth group takes a bus to E and finally arrives at the destination at the same time.

Set each group to walk for t hours, and then take bus 60? 5t50= 1.2-0. 1t hour,

According to the meaning of the question: 50 (t+1.2-0.1t)+5t× 4× 2 = 60× (4× 2-1),

Solution: t = 72 17.

Minimum time = t+1.2-0.1t =1.2+910× 7217 = 5185 (hours).

Answer: The shortest time is 5 185 hours.