JEE Main & Advanced Sample Paper JEE Main Sample Paper-45

  • question_answer
    A bag contains 10 black and 3 white balls. Balls are drawn one-by-one with out replacement till all the white balls are drawn. The probability that the procedure of drawing balls will come to an end at the seventh draw is

    A)  \[\frac{15}{286}\]                 

    B)  \[\frac{7}{286}\]

    C)  \[\frac{105}{286}\]                           

    D)  \[\frac{35}{286}\]

    Correct Answer: A

    Solution :

     Required probability = Probability of getting exactly two white balls and four black balls is 1 to 6th draw(X) probability of getting third white ball in 7th draw. \[=\frac{^{3}{{C}_{2}}{{\times }^{10}}{{C}_{4}}}{^{13}{{C}_{6}}}\times \frac{1}{7}=\frac{15}{286}\]

You need to login to perform this action.
You will be redirected in 3 sec spinner