A cyclist rides along a railway line with regular service. He is overtaken by a train every 30 minutes, and a train comes towards him every 20 minutes.
What is the interval of the train service?
Puzzle solution:
Imagine the cyclist rides along the railway line for one hour and then back again. In the first hour, three trains come towards him, and during the second hour, two trains overtake him. At the starting point, five trains per direction pass by in two hours, so the interval is 24 minutes (120 / 5 = 24).
How do you like this puzzle with the cyclist? Do you have any other solutions or comments? Feel free to write a comment...