Its fame is born from a gentle trap: intuition pushes towards an endless calculation of twists and turns, but the problem has a much more direct solution.
The fly between two trains
Riddle statement
Two trains are 300 km apart and are moving towards each other, each at 60 km/h.
A fly leaves the first train towards the second at 90 km/h. Every time it touches one train, it instantly turns and flies toward the other, repeating the process until the trains collide.
What total distance does the fly travel?