Elevator Paradox — first noted by George Gamow and Miritz Stern to explain why the first elevator car seems to be traveling in the opposite direction of where a user is trying to reach. They show a single elevator spends most of its time in the larger section of the building, and thus is more likely to approach from that direction when the prospective elevator user arrives.
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See also:
The Math Behind NUMB3RS — site produced by Wolfram Research specific to episodes they consult on for math concepts.