JEE Main & Advanced Mathematics Probability Question Bank Definition of probability

  • question_answer
    A and B toss a coin alternatively, the first to show a head being the winner. If A starts the game, the chance of his winning is                                              [MP PET 1987]

    A)                 5/8         

    B)                 1/2

    C)                 1/3         

    D)                 2/3

    Correct Answer: D

    Solution :

               The chance of head \[=\frac{1}{2}\] and not of head \[=\frac{1}{2}\]            Since \[A\] has first throw, he can win in the first, third, ?            \[\therefore \]Probability of A?s winning                    \[=\frac{1}{2}+{{\left( \frac{1}{2} \right)}^{2}}.\frac{1}{2}+{{\left( \frac{1}{2} \right)}^{4}}.\frac{1}{2}+........\]                                 \[=\frac{1}{2}+{{\left( \frac{1}{2} \right)}^{3}}+{{\left( \frac{1}{2} \right)}^{5}}+.........=\frac{2}{3}\].


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