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find the number of ways in which 12 people can be divided in

来源:学生作业帮 编辑:作业帮 分类:英语作业 时间:2024/11/06 04:53:51
find the number of ways in which 12 people can be divided into .
find the number of ways in which 12 people can be divided into three groups consisting of 4,4 and 3 people with one person excluded.
答案是69300
从12个人里面选4个人放在一组:12C4 = 495 种 
从剩下的8个人里面选4个人放在一组:8C4 = 70 种 
从剩下的4个人里面选3个人放一组:4C3 = 4 种 
一个人被排除在外的选法有:12 种 

总共方法数为 495 x 70 x 4 x 12 / 4! = 69300