1) There are 5 married couples at a party. The 5 men are blindfolded so that at the beginning of a certain song they have to pick one of the 5 women randomly to dance with her. What is the probability that at least one man selects his own wife?

2)If n people are present in a room. How large n need to be so that the probability of no two of them having their birthday on the same day is less than 2/3?