The Bird Trap.

Two trains each traveling at 30 km/hr are heading toward each other. Initially the trains are 60 km apart. Just then a bird on the front of one trains flies directly toward the other train at a speed of 60 km/hr ( relative to ground ) until it reaches the other train. It immediately turns and begins flying back toward the other train at the same speed until it meets that train, on and on it performs this bouncing back and forth until it is smashed to oblivion by the colliding trains ( no actual animals were harmed in the making of this puzzle - I think...).

What distance did the bird travel?

@joe-shmo said
Two trains each traveling at 30 km/hr are heading toward each other. Initially the trains are 60 km apart. Just then a bird on the front of one trains flies directly toward the other train at a speed of 60 km/hr ( relative to ground ) until it reaches the other train. It immediately turns and begins flying back toward the other train at the same speed until it meets that tr ...[text shortened]... imals were harmed in the making of this puzzle - I think...).

What distance did the bird travel?

The answer is Reveal Hidden Content, but that's not the real question. The real question is: where did I see this one before? Was it Carroll, or was it Hofstadter or Gardner? (In any case, I did not work out that answer myself.)

@Shallow-Blue

I think I first heard this anecdote:

When this problem was posed to John von Neumann, he immediately replied, "150 miles." "Ah, I see you've heard this one before, Professor von Neumann. Nearly everyone tries to sum the infinite series." "What do you mean?" asked von Neumann. "That's how I did it!"

Obviously the problem is tweaked slightly with distances and rates but I pulled this one from:

https://brilliant.org

If you want an pretty endless supply of puzzles its the place to be! For the most part I pretty much am sharing some of my highlight reel.