# I answered this for a LinkedIn brain teaser.  # On a sold out flight, 100 people line up to board # the plane. The first person in line has lost his # boarding pass, so he randomly chooses a seat. After # that, each person entering the plane sits in his # or her assigned seat, if it is available. If the # assigned seat is not available, the passenger chooses # an unoccupied seat randomly. You are the last passenger # to enter. What is the probability that you find your # assigned seat unoccupied?