排列、组合是中专数学教学中的难点之一,由于它的题型多,能力要求高,而且方法灵活,题目变化多端,因而学生在解这类问题时常常茫然不知所措。其实只要仔细分析题意,周密思考问题,正确运用加法原理、乘法原理,按照“分步相乘,分类相加,有序排列、无序组合”这一总原则,灵活地选用 Arrangement, combination of secondary school mathematics teaching is one of the difficulties, because of its many types of questions, high ability requirements, and flexible methods, subject changes, so students are often at a loss when solving this type of problem. In fact, as long as careful analysis of the ins and outs, careful thinking of problems, the proper use of addition principle, principle of multiplication, in accordance with the “principle of step-by-step multiplication, classification plus, orderly arrangement, disorderly combination”