1/15 of an hour is 4 minutes, and we know that it takes the city train 5 hours to go from the first stop to the last stop. And that the actual traveling time is 3 hours and the train stops at each stop for 1/15 hour. So basically, we have to find the ratio. 4 times 15 is 60, so 15 stops is an hour. Obviously , now 4 times 30 is 120, this is 120 minutes and 120 minutes makes 2 hours.
