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InterviewSolution
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A bag contains 3 white, 3 black and 2 red balls. One by one, threeballs are drawn without replacing them. Find the probability that the thirdball is red. |
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Answer» Correct Answer - `1//4` If third ball is red, then in first two draws, there will be either no red ball or one red ball. Let events `R_(0)=` in first two draws, red ball is drawn `R_(1)` = in first two draws, one red ball is drawn. `R=` in third draw , red ball is drawn. So, from total probability theorem, `P(R)=P(R_(0))P(R//R_(0))+P(R_(1))P(R//R_(1))` `=(""^(6)C_(2))/(""^(8)C_(2)).(""^(2)C_(1))/(""^(6)C_(1))+(""^(6)C_(1)""^(2)C_(1))/(""^(8)C_(2)).(""^(1)C_(1))/(""^(6)C_(1))` `=15/28.(2)/(6)+(6xx2)/(28).1/6=1/4` |
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