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.