At a movie theater, the manager announces that they will give a free ticket to the first person in line whose birthday is the same as someone who has already bought a ticket. You have the option of getting in line at any time. Assuming that you don't know anyone else's birthday, that birthdays are distributed randomly throughout the year, etc., what position in line gives you the greatest chance of being the first duplicate birthday?

from http://www.ocf.berkeley.edu/~wwu/riddles/hard.shtml

Assuming there are only 365 days in a year, and the birthdays are equally distributed in those days, one can maximize one's chance of getting the ticket by being the 20th person in line.  At that position, one would have a chance of winning of approximately 3.2319857549%.

Posted by Thalamus on 2004-03-29 13:36:54