The question here is:
What are the chances of any n people not having unique birthdays?
That's a difficult question. But the cool thing about probability is
that you can always find the probability of something by subtracting the
probability of its inverse from one. So instead, ask:
What are the chances of any n people having unique birthdays?
That would be:
(1/365) * ( 1/365 -1) * (1 /365 -2 ) * ... ( 1/365 - (n-1))
And once you have that, the answer to the original question is:
1 - ( (1/365) * ( 1/365 - 1 ) * ( 1/365 - 2) * ... ( 1/365 - (n-1)))
Now just plug in different values of n to find the odds of
n people not having unique birthdays.
