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排列、组合问题一直是高考中的热点,常以选择题、填空题的形式出现,属容易题的范畴,但学生在解这一类问题时却感到很棘手,失分也很多,如果在平时的学习中对排列、组合中的容易混淆的知识不加以重视,很容易造成错解.一、“加法原理”与“乘法原理”相混例一个口袋装有5个小球,另一个口袋装有4个小球,所有这些小球颜色互不相同.⑴从两个口袋内任取一个小球,有多少种不同的取法?⑵从两个口袋内各取一个小球,有多少种不同的取法?解析:⑴从两个口袋内任取一个小球有两类方法:第一
Arrangement, combination of questions has always been the hot college entrance examination, often multiple-choice questions, fill in the blank form, is a category of easy questions, but students in this type of problem is very tricky, lost a lot, if in peacetime Learning, the arrangement, the combination of the easy to confuse the knowledge do not pay attention to, it is easy to cause misunderstanding.A, “addition principle” and “principle of multiplication,” mixed with a pocket with five balls, The other pocket contains four small balls, all of which differ from each other in color. (1) How many different methods can be used to take a small ball from two pockets? (2) Take a ball from each of the two pockets, How many different ways to take? Analysis: (1) There are two ways to take a ball from two pockets: first