Q26:
How many different 6-letter sequences are there that consist of 1 A, 2 B’s, and 3 C’s ?
A. 6
B. 60
C. 120
D. 360
E. 720
怎么算?多谢!
P(6,6)/P(2,2)P(3,3)
=60
我是这么想的,先从6个位置里面选3个号给C,然后再从剩下的3个里面选2个给B,剩下1个就给A啦
因为c们与b们的位置是不用考虑的呀
所以c63.c32不知nn们说对不对
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