Suppose that the birthdays of different people in a group of n people are independent, each equally likely to be on the 365 possible days. (Pretend there's no such thing as a leap day.)
What's the smallest n so that it's more likely than not that someone among the n people has the same birthday as you? (You're not part of this group.)
At first, I get n=23 by using the complement rule to get the probability that someone has the same birthday as me (P{same birthday}=1−P{different birthday}) and use e−x=1−x.
But I don't think the answer is 23 since I am not part of the group.
Answer
HINT
The probability that none of the n people have the same birthday as you is:
(364365)n
So, set this equal to 12 and let WolframAlpha do its magic.
And as you alrady suspected, this problem is not like the infamous 'Birthday Problem'
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