将7人(含甲,乙)分成3组,一组3人,另两组2人,不同的分组数为M,甲,乙分在同一组的概率为N,则M,N分别为 ( )A.105; 5/21 B.105; 4/21 C.210; 5/21 D.210; 4/21
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![将7人(含甲,乙)分成3组,一组3人,另两组2人,不同的分组数为M,甲,乙分在同一组的概率为N,则M,N分别为 ( )A.105; 5/21 B.105; 4/21 C.210; 5/21 D.210; 4/21](/uploads/image/z/3869592-24-2.jpg?t=%E5%B0%867%E4%BA%BA%28%E5%90%AB%E7%94%B2%2C%E4%B9%99%29%E5%88%86%E6%88%903%E7%BB%84%2C%E4%B8%80%E7%BB%843%E4%BA%BA%2C%E5%8F%A6%E4%B8%A4%E7%BB%842%E4%BA%BA%2C%E4%B8%8D%E5%90%8C%E7%9A%84%E5%88%86%E7%BB%84%E6%95%B0%E4%B8%BAM%2C%E7%94%B2%2C%E4%B9%99%E5%88%86%E5%9C%A8%E5%90%8C%E4%B8%80%E7%BB%84%E7%9A%84%E6%A6%82%E7%8E%87%E4%B8%BAN%2C%E5%88%99M%2CN%E5%88%86%E5%88%AB%E4%B8%BA+%28+%29A.105%3B+5%2F21+B.105%3B+4%2F21+C.210%3B+5%2F21+D.210%3B+4%2F21)
将7人(含甲,乙)分成3组,一组3人,另两组2人,不同的分组数为M,甲,乙分在同一组的概率为N,则M,N分别为 ( )A.105; 5/21 B.105; 4/21 C.210; 5/21 D.210; 4/21
将7人(含甲,乙)分成3组,一组3人,另两组2人,不同的分组数为M,甲,乙分在同一组的概率为N,
则M,N分别为 ( )
A.105; 5/21 B.105; 4/21 C.210; 5/21 D.210; 4/21
将7人(含甲,乙)分成3组,一组3人,另两组2人,不同的分组数为M,甲,乙分在同一组的概率为N,则M,N分别为 ( )A.105; 5/21 B.105; 4/21 C.210; 5/21 D.210; 4/21
M=C(7,3)C(4,2)C(2,2)/A(2,2)=105
甲乙分在同一组的情况有:C(5,1)C(4,2)C(2,2)/A(2,2)+C(5,3)C(2,2)=25
∴N=25/105=5/21
选A
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