袋中有2个黑球4个白球,从中任取3个球中恰有3个白球的概率为___________.
人气：326 ℃ 时间：2020-05-06 02:13:32
解答
答案为1/5,即将从四个白球中取三个白球的种类（4）除以在六个球中取三个球的种类（20）即得到答案.
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