JEE Main & Advanced Mathematics Probability Question Bank Self Evaluation Test - Probability-II

  • question_answer
    There are n letters and n addressed envelopes, the probability that all the letters are not kept in the right envelope, is

    A)  \[\frac{1}{n!}\]

    B) \[1-\frac{1}{n!}\]

    C) \[1-\frac{1}{n}\]

    D) None of these

    Correct Answer: B

    Solution :

    [b] Probability of all the letters kept in the right envelope is \[\frac{1}{n!}\](\[\because \]Total letters = n) i.e., \[P=\frac{1}{n!}\] We know, if q is the term used for the probability of the letters which are not kept in the right envelope. Then \[p+q=1\Rightarrow q=1-p=1-\frac{1}{n!}.\]


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