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Friday Riddle Answer

nudgie's picture
Posts: 1482
Joined: Sep 2006

RIDDLE: A line of 100 airline passengers is waiting to board a plane. They each hold a ticket to one of the 100 seats on that flight. (For convenience, let's say that the nth passenger in line has a ticket for the seat number n.)
Unfortunately, the first person in line is crazy, and will ignore the seat number on their ticket, picking a random seat to occupy. All of the other passengers are quite normal, and will go to their proper seat unless it is already occupied. If it is occupied, they will then find a free seat to sit in, at random.
What is the probability that the last (100th) person to board the plane will sit in their proper seat (#100)?

ANSWER: The whole things stops whe someone else sits in Crazy Guy's seat. The chances of that range from 1/99 (first person) to 1/1 for thelast guy, so, 1/99, summation from 98 of 2 of (1/ n (n+1) )

This returns 0.5 (50%)

Also, the answer remains 50% no matter how many people are added to the line

Lori-S's picture
Posts: 1286
Joined: Sep 2010

I got it right with my twisted logic. Applause please

Not to mention I paid a lot of money for a degree in twisted logic so it's good to see some kinda return on that.

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