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.16OO B. 3600 C. 1260 D. 2460
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.16OO B. 3600 C. 1260 D. 2460
答
A有3种放法,4,3,2任选一
B有2种放法,因为被A选了一种
C就只剩一种放法了
所以
3+2+1=6
答
6种
答
C（下9上4）*C（下5上3）*C（下2上2）=1260
答
没法给你打出来啊，你就凑合着看吧
{C4（9）}*{C3（5）}*{C2（2）}