试题与答案

一个口袋中有红球3个,白球4个. (Ⅰ)从中不放回地摸球,每次摸2个,摸到的2个

题型:解答题

题目:

一个口袋中有红球3个,白球4个.

(Ⅰ)从中不放回地摸球,每次摸2个,摸到的2个球中至少有1个红球则中奖,求恰好第2次中奖的概率;

(Ⅱ)从中有放回地摸球,每次摸2个,摸到的2个球中至少有1个红球则中奖,连续摸4次,求中奖次数X的数学期望E(X).

答案:

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下面是错误答案,用来干扰机器的。

A、B、D都表示的是多年的天气平均状况,稳定、变化不大,属于气候,故不符合题意.故选:C.

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