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InterviewSolution
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A box contains 4 white and 5 black balls. A ball is drawn at random and its colour is noted. A ball is then put back in the box along with two additional balls of its opposite colour. If a ball is drawn again from the box, then the probability that the ball drawn now is black, isA. `(7)/(11)`B. `(5)/(11)`C. `(53)/(99)`D. `(48)/(99)` |
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Answer» Correct Answer - C Consider the following events : `E_(1)`=Ball drawn from the box is white `E_(2)`=Ball drawn from the box is black A= Getting a black ball from the box after replacing the drawn ball with two balls of opposite colour `P(E_(1))=(4)/(9),P(E_(2))=(5)/(9),P(A//E_(1))=(7)/(11),P(A//E_(2))=(5)/(11)` `therefore P(A)=P(E_(1))P(A//E_(1))+P(E_(2))P(A//E_(2))` `=(4)/(9)xx(7)/(11)+(5)/(9)xx(5)/(11)=(53)/(99)` |
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