Brain Teasers & Mental Math
100 passengers board a full 100-seat plane. Passenger 1 lost his ticket and sits in a random seat. Each later passenger takes their own seat if free, otherwise a random free seat. What is the probability passenger 100 gets their own seat?
Model answer
1/2.
Key observation: the chaos ends the moment anyone sits in seat 1 (everyone after gets their own seat) or in seat 100 (the last passenger is displaced). Every 'random' chooser is equally likely…
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