The speed of a freight train is 60 km / h. What is its length in meters if it is known that it passes by a stationary observer in 15 s?

1. Since 1 hour = 60 minutes = 3600 seconds, therefore, we can write down how much of an hour is 15 seconds.
1/3600 * 15 = 15/3600 hours.
2. We know that the speed of the train is 60 km per hour, therefore we can calculate the length of the train, which in 15/3600 hours passes by a stationary observer.
60 * 15/3600 = 900/3600 = 0.25 km or 250 meters.
Answer: The length of the train is 250 meters.