9本书,放在A,B,C三个柜子上,分别放4本,3本,2本,有几种放法
问题描述：
9本书,放在A,B,C三个柜子上,分别放4本,3本,2本,有几种放法
拜托,很急
我还是把原题打出来吧
In how many ways cahatn 9 different books be divided among three boys A,B and C so that they receive 4 ,3 and 2 books respectively?
A.16OOB. 3600 C. 1260 D. 2460
答
C（下9上4）*C（下5上3）*C（下2上2）=1260