分类计数原理与分步计数原理是学好排列组合这一章的基础和关键,同时也是排列组合这一章非常重要的一部分内容,所以高考对这两个原理的考查贯穿于这一章的始终·而在高考中,又经常设计单独考查这两个 Categorical counting principle and the principle of fractional counting is the basis and key to learn to arrange the combination of this chapter is also a very important part of the arrangement of the chapter, so the college entrance examination of these two principles throughout this chapter has always been In college entrance examination, and often designed to test these two alone