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This is a Math question I read and I badly want to know the answer. It says; There are twelve people who own 12 phones.One of them(who owns the most valuable phone) suggested to write down their names and the phone model on billets and toss them.Then to exchange the phones according to the phone model on the billets they received after the tossing. The questions is;what is the probability of not receiving the same billet which is written by himself(or herself)?

And the answer I suggested is 11/12;which is wrong!

Can someone help me with this? Thank you in advance.

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    The question is a little foggy, imo: What is the probability of *who* not receiving his own billet? Does everybody get at the same time a billet or they draw them by turn out of a bowl or something? Is the question perhaps "what's the prob. that *exactly*, *at least one*, *at most one* receives his own...etc.?2012-11-14
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    The person with the valuable phone is being generous! The probability that a particular person, say Alicia, does not receive her own phone is indeed $11/12$. But maybe the question is "what is the probability **no one** gets her own phone." Then the solution is quite a bit harder. It is, however, a standard problem with a very nice answer.2012-11-14

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