Question

in a family of four, what is the probability that no two people have birthdays in the same month? (please assume that all months have equal probability.)

Answer 1

First of all, you should mention that the 4 persons respective dob's are not known to you because if their dob's are known before hand, then there is no probability (because the outcome is known to you).

By assuming that we don't know their dob's, we proceed to the problem.