48. 100 students are heading to a youth palace 33 kilometers away from the school. There is only one car that can carry 25 people. To ensure that all students reach the destination as quickly as possible, it is decided to combine walking and riding. It is known that the students' walking speed is 5 kilometers per hour, and the car's speed is 55 kilometers per hour. To ensure that all students arrive at the destination as quickly as possible, the required time is $\qquad$ hours. (The time for getting on and off the car is not considered).
answer: 2.6