Nice solutions, but it's not actually stated in the question that there are 100 passenger seats. Hence you have jumped into "maths world" where because there are numbers you assume it must be a sum.
In the real world, any displaced passenger says "you're in my seat."
In the real world, airlines overbook and you might have 100 passengers with "pre-booked seats" for a 90-seat plane.
Allan
-----Original Message-----
From: A UK-based worldwide e-mail broadcast system mailing list on behalf
of Suhal Bux
Sent: Wed 1/30/2008 16:23
To: [log in to unmask]
Subject: Airplane riddle
Hello
I know this isn't strictly the right sort of post but it's interesting
and is doing my head in...
100 passengers are queuing to get on a plane.
Each has a ticket with a seat number and they are standing in order.
The first man in the queue is crazy and will sit anywhere at random.
The rest of the passengers will sit in their own seat, unless it is not
available, in which case they will sit in another seat at random.
What is the probability that the 100th passenger sits in his own seat?
I'd appreciate proofs or good reasoning.
The best most correct answer gets a special prize (a McDonald's
voucher!).
Regards
Suhal Bux
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