JEE Main & Advanced Mathematics Probability Question Bank Use of permutations and combinations in probability

  • question_answer
    A fair coin is tossed 100 times. The probability of getting tails an odd number of times is

    A)          \[\frac{1}{2}\]                       

    B)            \[\frac{1}{8}\]

    C)            \[\frac{3}{8}\]                          

    D)            None of these

    Correct Answer: A

    Solution :

                       The total number of cases are \[{{2}^{100}}\]                    The number of favourable ways                                 \[{}^{100}{{C}_{1}}+{}^{100}{{C}_{3}}+\,.......\,+{}^{100}{{C}_{99}}={{2}^{100-1}}={{2}^{99}}\]                    Hence required probability \[=\frac{{{2}^{99}}}{{{2}^{100}}}=\frac{1}{2}.\]


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