一类古典概型概率的计算

A Class of Classical Probabilities

设X1,X2,…,Xn为n个随机变量,为求概率P(X1+X2+…+Xn)=r,利用母函数方法,将其关键步骤转化为判定一个n元一次不定方程正整数解个数的问题,并借助实例加以说明.

Let X1 ,X2 ,… ,Xn be n random variables. To calculate the possibility P（X1 ＋X2 ＋…＋Xn）= r, We use generating function and count the number of positive integer solutions of alinear indeterminate equation of n,variables. ExampleS are illustrated.