John von Neumann — the man who created game theory, advanced many branches of mathematics and physics, and did more than anyone to design the modern computer — was someone who attracted a certain amount of mythology.
One story about von Neumann has a colleague setting him a fun puzzle. In this puzzle, two trains, 20 miles apart, chug slowly towards each other down a single track. A fly starts at the front of one train and zips off towards the other, then instantly turns around and zips back again. Back and forth goes the fly, until the trains smash into each other, squashing it between them.
The fly travels at 15mph, and each train puffs along at 10mph. How far does the fly travel before being squashed?
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