[理工] 機率
At a party,n men and m women put their drinks in a table and
go out on the floor to dance. When they return, none of them
recognizes his or her drink,so everyone takes a drink at random.
What is the probability that each man selects his own drink?
我的想法是一開始男生的飲料有n杯桌上共m+n杯
所以第一個人取得自己飲料的機會是1/m+n
第二個人取得自己飲料的機會是1/m+n-1
.....所以n個男生取得飲料的機會是1/(m+n)(m+n-1) ... (m+n-(n-1))
答案是m!/(m+n)!
請問一下我哪裡想錯了
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