题目网址: http://www.puzzleup.com/2016/
http://www.puzzleup.com/2016/puzzle/?11
答题时限: 10月６日７ＰＭ－比赛结束（约12月14日）
加分时限: 10月６日７ＰＭ－10月12日６：５９ＰＭ
答对可得基本分１００分。答案可上传５次，每改１次答案从基本分扣２０分。　
比赛期间内可随时上传答案，加分时限内答对第ｎ天加（６－ｎ）分　 　　 　　
另依题目的难易有额外加分（如有８０％的人这题答错，答对者加８０分）　　
◆PROBABILITY OF RAIN
If the probability of rain on exactly 5 days in a week is the same as the
probability of rain on exactly 6 days in a week what is the probability of
rain on a day?
Notes:
- The probability of rain on each day is the same, and it is greater than
zero, and smaller than one.
- The days with rain (5 days and 6 days) can be in any order.
Enter your answer as a simplified fraction. Example:12/23
若一周内恰好五天下雨的机率和一周内恰好六天内下雨的机率相等，
则一天下雨的机率是多少？
注:
* 此“一天下雨的机率”是固定的，且大于零并小于一。
* 实际下雨日子 (即这五天或六天) 可以是任意组合。
以最简分数回答，如 12/23。
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又是高中机率题...