agree~~~

來源: cheerleaders 2010-04-23 17:13:05 [] [博客] [舊帖] [給我悄悄話] 本文已被閱讀: 次 (578 bytes)
本文內容已被 [ cheerleaders ] 在 2010-04-25 08:03:23 編輯過。如有問題,請報告版主或論壇管理刪除.
There are 7 people and 30 days in April. Assuming distribution of birth dates is completely random, choose one person. That person's birth date does not matter. The second person has a 29/30 chance of having a different birth date. The third person has a 28/30 chance of having a different birth date than the first and second persons. Repeat until the seventh person has a 24/30 chance of having a different birth date. Multiply to get the chance that all the birth dates will be different. Subtract from 1 to get the probability that at least one birth date will be repeated.
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