1. On a path parallel to the railway, a group of people and cyclists were driving south at the same time. The pedestrian speed is 3.6 km/h, and the cyclist speed is10.8 km/h. At this moment, a train comes from behind them. It takes 22 seconds for a train to overtake pedestrians and 26 seconds for a cyclist. What is the total length of the train?

Analysis: this topic is called catching up. The pedestrian speed is 3.6 km/h = 1 m/s, the cyclist speed is 10.8 km/h =3 m/s, and the length of the train body is equal to the distance difference between the train tail and pedestrians, as well as the distance difference between the train tail and cyclists. If the speed of the train is assumed to be x m/s, the length of the train body can be expressed as (x- 1)×22 or (x-3)×26, so it is not difficult to list the equations.

Solution: Let the speed of this train be x m/s, and make an equation according to the meaning of the question.

(x- 1)×22=(x-3)×26 .

The solution is x= 14. So the body length of the train is

( 14- 1)×22=286 (m)。

A: This train is 286 meters long.

2. Solution: Let the low-order two-digit number be X and the high-order two-digit number be Y..

x=5y+4

100x+y= 100y+x+7920

The solution is x=99.

y= 19

A: The original four digits were 1999.