排列组合中的分组问题

The Problem of Dividing N Different Elements into Groups in Permulation and Combination

将n个不同的元素分成m个组 (n≥m) ,计算其不同分组的种数是中学生易出错的问题。本文初探此问题的六种情况。

It is difficult for students to calculate how many kinds of methods there are to divide N different elements into M different groups (N is not less than M).In the paper,the author has discussed initially six different kinds of situations about the question and induced respective formulas.