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

  • question_answer
    A committee has to be made of 5 members from 6 men and 4 women. The probability that at least one woman is present in committee, is

    A)            \[\frac{1}{42}\]                       

    B)            \[\frac{41}{42}\]

    C)            \[\frac{2}{63}\]                       

    D)            \[\frac{1}{7}\]

    Correct Answer: B

    Solution :

                       Total number of ways                    \[={}^{4}{{C}_{1}}\times {}^{6}{{C}_{4}}+{}^{4}{{C}_{2}}\times {}^{6}{{C}_{3}}+{}^{4}{{C}_{3}}\times {}^{6}{{C}_{2}}+{}^{4}{{C}_{4}}\times {}^{6}{{C}_{1}}+{}^{6}{{C}_{5}}\]                    \[=60+120+60+6+6=252\]                    No. of ways in which at least one woman exist are                    \[={}^{4}{{C}_{1}}\times {}^{6}{{C}_{4}}+{}^{4}{{C}_{2}}\times {}^{6}{{C}_{3}}+{}^{4}{{C}_{3}}\times {}^{6}{{C}_{2}}+{}^{4}{{C}_{4}}\times {}^{6}{{C}_{1}}=246\]                    Hence required probability \[=\frac{246}{252}=\frac{41}{42}\].


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