Talk about the encounter between the express train and the local train.

The time for people sitting on the express train to see the local train pass is 1 1 sec, which is not only a matter of picking up people from the local train, but also the speed of the express train. The meeting distance is 385m, and the meeting time is 1 1 sec. That is, the sum of the speed of people and the local train is: 385÷ 1 1=35 (m/s). Then, when people sitting on the local train see the passing time of the express train, it's not just a matter of people meeting the express train. People have the speed of the local train at this time, and the distance of meeting is 280 meters, that is, the sum of the speed of people and the express train is the local train.