通过对这两年全国各地近300份中考数学试题的研究,我们发现,有不少试卷里设计了运用概率模型解释、判断游戏是否公平的问题.略举几例.例1(2013年杭州)某班有50位学生,每位学生都有一个序号,将50张编有学生序号(从1号到50号)的卡片(除序号不同外其它均相同)打乱顺序重新排列,从中任意抽獉獉獉取獉1獉张獉卡片.(1)在序号中,是20的倍数的有:20,40,能整除20的有:1,2,4,5,10(为了不重复计数,20只计一次),求取到的卡片上序号是20的倍数或能整除20的概率;(2)若规定:取到的卡片上序号是k(k是满足1≤k≤50的整数),则序号是k的倍数或 Through the research on nearly 300 middle school math test questions throughout the country in these two years, we find that there are many papers designed to explain the game using the probability model to explain whether the game is fair, to name a few examples 1 (Hangzhou 2013) A class of 50 students, each student has a serial number, the 50 compiled with the student number (from 1 to 50) card (except for the serial number is the same) disorderly rearrange the order, arbitrarily from 1 獉 獉 獉 獉 1 獉 Zhang 獉 card. (1) in the serial number, is a multiple of 20 are: 20,40, divisible by 20 are: 1,2,4,5,10 (in order not to repeat the count, 20 counted once), the card number is obtained is a multiple of 20 or the probability of divisible by 20; (2) If the provisions of: the card number is k (k is an integer satisfying 1 ≤ k ≤ 50) , Then the serial number is a multiple of k or