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When a certain coin is flipped, the probability of heads is 0.5. If the coin is flipped 6 times, what is the probability that there are exactly 3 heads?
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当前版本由 Helen 更新于2019-01-05 16:03:11 感谢由 Helen 对此题目的解答所做出的贡献。
每次抛硬币出现正面和反面的概率都是0.5（或者说1/2），那么抛6次硬币恰好3次是正面的概率是P=C(6,3)*(1/2)^6=20/64=5/16
当前版本由 志在320 更新于2018-12-02 16:49:39 感谢由 志在320 对此题目的解答所做出的贡献。
每投掷一次硬币，有两种可能，连续投掷六次，彼此互补相干，则总共有2^6=64中情况，现在，要求其中三个是面朝上的，用排列组合知识，六个里面选三个有20中情况，所以面朝上的概率为20/64=5/16
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