锅中有芝麻汤圆6个,花生汤圆5个,豆沙4个,三个汤圆外部特征一致,从中任意瑶4个,则每种汤圆至少1个概率
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每种汤圆至少1个概率为

(C(6,2)*C(5,1)*C(4,1)+C(6,1)*C(5,2)*C(4,1)+C(6,1)*C(5,1)*C(4,2))/C(15,4)

=(15*5*4+6*10*4+6*5*6)/1365

=(300+240+180)/1365

=720/1365

=48/91