n只球(1~n号)随机放入n个盒子1~n号),每盒一只,求任意球号均不与盒号相等的概率.n只球(1~n号)随机放入n个盒子1~n号),每盒一只,求任意球号均不与盒号相等的概率,
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n只球(1~n号)随机放入n个盒子1~n号),每盒一只,求任意球号均不与盒号相等的概率.n只球(1~n号)随机放入n个盒子1~n号),每盒一只,求任意球号均不与盒号相等的概率,
n只球(1~n号)随机放入n个盒子1~n号),每盒一只,求任意球号均不与盒号相等的概率.
n只球(1~n号)随机放入n个盒子1~n号),每盒一只,求任意球号均不与盒号相等的概率,
n只球(1~n号)随机放入n个盒子1~n号),每盒一只,求任意球号均不与盒号相等的概率.n只球(1~n号)随机放入n个盒子1~n号),每盒一只,求任意球号均不与盒号相等的概率,
设X(n)=n只球放入n个盒子任意球号均不与盒号相等的方法总数
有X(n)=(n-1)*[X(n-1)+X(n-2)]
其概率P(n)=X(n)/n!P(n)=(n-1)*[P(n-1)*(n-1)!+P(n-2)*(n-2)!]/n!
X1=0;P1=0
X2=1;P2=1/2
X3=2;P3=2/6=1/3
X4=9;P4=9/24
X5=44;P5=44/120
X6=265;P6=265/720
X7=1854;P7=1854/5040
.
设N个球放入与盒号相等的概率为p,则题目求1-p
放入的球号与盒号相同的概率:p=(1/n)X [1/(n-1)] X[1/(n-2)].....x1=(1/n)!
故,题求概率P=1-p =1-(1/n)!
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