题目网址: http://www.puzzleup.com/2013/ http://www.puzzleup.com/2013/puzzle/?261 答题时限: 12月５日７ＰＭ－比赛结束 加分时限: 12月５日７ＰＭ－12月９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）　　 ◆Twelve Numbers There are twelve cards which are numbered from 1 to 12. You shuffle the cards, and open them one by one. For each card, if the card has a number larger then all previous cards, you score 1 point. After all the cards are opened, the sum of the scores is your total score. If you repeat this operation many times, what would be the average of your total score. Note: For the first card you score 1 point directly. (If your answer is not an integer, enter it with two digits after the decimal point without rounding.) 有十二张牌编号由 1 至 12。你将这些牌洗牌，再将其一一翻开。 若每张牌翻开时它比所有目前已翻开的牌都大，则你得一分。 在所有卡都翻开後，所有分数和就是你的总分。 若重覆这个动作许多次，问总分的平均是多少？ 注: 第一张牌翻开时直接获得一分。 (译注: 即是说第一张牌比目前是空集合的「所有」已翻开的牌大，故得分) 若答案不是整数，则无条件舍去到小数後第二位。 -- 'Oh, Harry, don't you see?' Hermione breathed. 'If she could have done one thing to make absolutely sure that every single person in this school will read your interview, it was banning it!' ---'Harry Potter and the order of the phoenix', P513 --

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