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Re: Birthday Chances

by tahnead (Initiate)
on Jul 16, 2007 at 05:09 UTC ( #626776=note: print w/replies, xml ) Need Help??


in reply to Birthday Chances

what are the chances of this..... plz someone help!! a group of 30 co-workers 2 are born on 19 may, different years 2 are born on 31 july, different years 4 are born on 17 march, and of those 2 have the same years!

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Re^2: Birthday Chances
by Anonymous Monk on Jul 29, 2010 at 22:55 UTC

    Well if you just use the idea that choosing 2 people out of a group has a certain number of possibilities, it would stand to reason when the possibilities get larger than 366, you are probably going to have two people with the same birthday. If you choose two people out of a group of 28 people, there are 378 ways to do this without repeats! That makes the odds pretty good that two of them with have the same birthday.

      it would stand to reason when the possibilities get larger than 366, you are probably going to have two people with the same birthday

      Not probably but definitely.

      If you have a group of 366 (or more) people you always have 2 people that share the same birthday (assuming a non-leap year).

      This reasoning is called "pigeonhole principle".

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