关于排列与组合中的分组问题,有有序、无序、均匀、部分均匀、非均匀、指定分配、无指定分配等不同的分组问题。这些问题常使一些中学生感到困难,为此,特编选三个典型例题并给出相应问题的一般结论,供解决有关分组问题时参考。问题一把21本不同的书,分给 2) With regard to the grouping problem in permutation and composition, there are different grouping issues such as order, disorder, uniformity, partial uniformity, non-uniformity, designated allocation, and no specified allocation. These problems often make some middle school students feel difficult. To this end, we have specially selected three typical examples and given the general conclusions of the corresponding questions for reference when solving the grouping problem. A 21 different book, divided into 2)