@aviationdoctor.eth

There's a famous one about von Neumann, though possibly apocryphal. von Neumann was asked: Two trains 100 miles apart are moving toward each other, each at a speed of 50 mph. A fly starting at the front of one of the trains flies back and forth between them at a speed of 75 mph. It does this until the trains collide and crush the fly. What is the total distance the fly has flown? There's a trivial way to answer this (the trains will take one hour to collide, so the fly will have flown 75 miles). But mathematicians may fall into the convoluted trap of thinking of the pattern of the fly bouncing off each train at ever-decreasing distances, turning that into a converging infinite series, and summing it up. When asked, Neumann took just a few seconds and responded with the correct answer. The interviewer congratulated him for not falling into the trap. To which von Neumann responded, "what trap? You just need to sum the infinite series"

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