It takes 20 seconds for a train to run at a constant speed through a 450m long tunnel. There is a light on the tunnel, and the time for the light to shine on the train is 5S Ask: (1) the length of the train; (2) the time that the train runs completely in the tunnel There is a light in the tunnel. The time that the light shines on the train is 5S. What do you mean///////

It takes 20 seconds for a train to run at a constant speed through a 450m long tunnel. There is a light on the tunnel, and the time for the light to shine on the train is 5S Ask: (1) the length of the train; (2) the time that the train runs completely in the tunnel There is a light in the tunnel. The time that the light shines on the train is 5S. What do you mean///////

Let the unknowns be x, the length of the train is Y M / s, x + 450 = 20Y, 5Y = x (1) x = 150m, y = 30m / s
(2)(450-150)/30=10
The length of the train is 150m and the running time is 10s
There is a lamp in the tunnel. The time that the lamp shines on the train is 5S. That is to say, it takes 5S for the train to pass through the lamp from the front to the rear, so the speed x5s = the length of the train

It takes 20 seconds for a train to run at a constant speed through a 450m long tunnel. There is a light on the tunnel, and the time for the light to shine on the train is 5S. Why do you use the train length / time when the light shines on the top of the train?

When a train passes through a tunnel, it is necessary to consider that the front of the train enters the tunnel and the rear of the train leaves the tunnel
Consider the length of the train and the length of the tunnel
The light on the train, just need to consider the length of the train and speed