find the number of ways in which 12 people can be divided into .
问题描述：
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
答
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