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解排列、组合混合问题时,一股思考原则是:先选元素,后排列。同时,必须正确理解和使用加法原理及乘法原理,对要处理的问题进行合理的分类和分步,以免产生“重复”或“遗漏”现象。例如有这样一道题:按下列要求分配六本不同的书,各有几种方法:(1)平均分给甲、乙、丙三人;(2)平均分成三份;(3)分成三份:一份一本,一份二本,一份三本;(4)分给甲、乙、丙三人:一人一本,一人二本,一人三本;(5)分成三份,一份四本,一份一
When unmarshalling and combinatorial problems are mixed, one principle of thinking is: first select the elements and then arrange them. At the same time, we must correctly understand and use the principle of addition and principle of multiplication, and classify and classify the problems to be dealt with in order to avoid “repetition” or “missing” phenomena. For example, there is such a question: Six different books are allocated according to the following requirements, each of which has several methods: (1) average points to three persons in A, B, and C; (2) average in three parts; (3) in three parts : One copy, one copy and two copies, three copies; (4) Credits to A, B, and C: one copy for one person, two copies for one person, and three copies for one copy; (5) divided into three copies, one copy Four books, one copy