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

  • question_answer
    In an examination, the probability of a candidate solving a question is \[\frac{1}{2}.\] Out of given 5 questions in the examination, what is the probability that the candidate was able to solve at least 2 questions?

    A) \[\frac{1}{64}\]

    B) \[\frac{3}{16}\]

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

    D) \[\frac{13}{16}\]

    Correct Answer: D

    Solution :

    [d] \[P{{=}^{5}}{{C}_{2}}{{\left( \frac{1}{2} \right)}^{2}}{{\left( \frac{1}{2} \right)}^{3}}{{+}^{5}}{{C}_{3}}{{\left( \frac{1}{2} \right)}^{3}}{{\left( \frac{1}{2} \right)}^{3}}\] \[{{+}^{5}}{{C}_{4}}{{\left( \frac{1}{2} \right)}^{4}}{{\left( \frac{1}{2} \right)}^{1}}{{+}^{5}}{{C}_{2}}{{\left( \frac{1}{2} \right)}^{5}}{{\left( \frac{1}{2} \right)}^{0}}\] \[={{\left( \frac{1}{2} \right)}^{5}}\left[ ^{5}{{C}_{2}}{{+}^{5}}{{C}_{3}}{{+}^{5}}{{C}_{4}}{{+}^{5}}{{C}_{5}} \right]\] \[=\frac{1}{{{3}^{2}}}\times 26=\frac{13}{16}.\]


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