为贯彻“激情工作,快乐生活”的理念,某单位在工作之余举行趣味知识有奖竞赛,比赛分初赛和决赛两部分.为了增加节目的趣味性,初赛采用选手选一题答一题的方式进行,每位选手最多有5次选题答题的机会,选手累计答对3题或答错3题即终止其初赛的比赛,答对3题者直接进入决赛,答错3题者则被淘汰.已知选手甲答题的正确率为 . (1)求选手甲答题次数不超过4次可进入决赛的概率; (2)设选手甲在初赛中答题的个数为 X ,试写出 X 的分布列,并求 X 的数学期望.
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举一反三
【单选题】The time interval on the leading edge of a pulse between 10% and 90% of the amplitude is the ( ).
【简答题】读一读,写出人物姓名。 Bart is drawing on the blackboard. Lisa is singing. Matt is jumping on the desk. Mary is eating. Mark is playing the ball with Lucy. 1. ______________2. ______________3. ______________4. _...
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