排列组合问题是每年高考的必考内容,其考查形式绝大多数以选、填题的形式出现,试题的难度一般以中档题为主.由于排列组合试题知识相互交错,综合性强,思路灵活,解答时往往容易将二者的概念 Permutations and combinations of the annual college entrance examination is the compulsory examination content, most of the test form to choose, fill in the form of the difficulty of the questions are generally dominated by mid-range questions. As arranged knowledge of the combination of questions intertwined, comprehensive, flexible thinking , The solution is often easy to put the concept of the two