Due to the stimulating questions here, this question might have been posted earlier. Sorry if it has. Also this question involves an airplane. I just used the word "plane" for the alliteration.
There are 100 people on a plane. Let's label them Persons 1-100. The order the people sit down is determined by his or her seat number. There are 100 seats, labeled Seats 1-100. Person 1 does not know where to sit and will sit in any random passenger seat. Persons 2-100 are assigned to their corresponding seat number and will sit there. If someone is already sitting at the assigned seat, the person would sit at a random unoccupied passenger seat. Here's an example:
Person 1 sits in seat 5
Person 2 sits in Seat 2
Person 3 sits in Seat 3
Person 4 sits in Seat 4
Person 5 sits in Seat 7
Person 6 sits in Seat 6
Person 7 sits in Seat 1
This is just one example of what might happen. The question is: What is the probability that Person 100 sits in Seat 100?
If there are any unclear parts please feel free to ask. I doubt i have left anything out, but if I did, please feel free to say so.
If this isn't solved by tomorrow, I'll give a hint.