11. An express train and a local train run in opposite directions. The length of the express train is 280 meters and the length of the local train is 385 meters. It takes one hour for people sitting on the express train to see the local train How many seconds does it take for people on the local train to see the express passing?

11. An express train and a local train run in opposite directions. The length of the express train is 280 meters and the length of the local train is 385 meters. It takes one hour for people sitting on the express train to see the local train How many seconds does it take for people on the local train to see the express passing?

The relative speed of the two trains is 385 / 11 = 35 m / s because people on the express train watch the local train run for 11 seconds
So on the local train, it takes 280 / 35 = 8 seconds for the express to pass
No, ask me

A fast train and a slow train are running in opposite directions. The fast train is 200 meters long and the slow train is 250 meters long. When people sitting on the fast train see the slow train driving for 10 seconds, that's the best time
A fast train and a slow train run in opposite directions. The fast train is 200 meters long and the slow train is 250 meters long. It takes 10 seconds for people sitting on the fast train to see the slow train passing by, so how many seconds does it take for people sitting on the slow train to see the fast train passing by?
What's the formula

It takes 10 seconds for people on the express train to see the local train passing by, which means that the relative speed of the two trains is:
250/10=25m/sec.
It can be seen that the time when people on the local train see the express passing by is:
200/25m=8sec
The answer is: 8 seconds