mohican Posted June 17, 2005 Share Posted June 17, 2005 Total 6 balls, 2 Red, 2 Blue and 2 Green. If the probability of neither draw turning up a blue ball (i.e. no blue balls at all) 4/6 * 3/5 = 12/30 = 2/5 (without replacement) then , With replacement why the probability of neither draw turning up a blue ball (i.e. no blue balls at all) it is not 4/6 * 4/6 = 16/36 = 4/9 ? Quote Link to comment Share on other sites More sharing options...
800ForSure Posted June 17, 2005 Share Posted June 17, 2005 Mohican, I am not sure what do you want to know...but in the second case of OA is not giving you the right answer then may be check if the balls are being picked one by one or together... Else post the original question and let the TMs...solve it for you Quote Link to comment Share on other sites More sharing options...
mohican Posted June 17, 2005 Author Share Posted June 17, 2005 Ok, what I am trying to ask is There are 6 marbles in a bag. 2 are red, 2 blue and 2 green. Two marbles are drawn randomly with replacement. What the probability that atleast one of them is blue? Quote Link to comment Share on other sites More sharing options...
he_hels Posted June 17, 2005 Share Posted June 17, 2005 Blue both times: 2/6*2/6 Blue only first : 2/6*4/6 Blue only second : 4/6*2/6 Sum it up: 5/9 Quote Link to comment Share on other sites More sharing options...
mohican Posted June 17, 2005 Author Share Posted June 17, 2005 I agree with you, but somebody was saying it to be 8/9. Quote Link to comment Share on other sites More sharing options...
rd_eastbay Posted June 19, 2005 Share Posted June 19, 2005 Nope : 1 - 4/9 = 5/9. Quote Link to comment Share on other sites More sharing options...
800ForSure Posted June 19, 2005 Share Posted June 19, 2005 No Blue at all = 4/6 * 4/6 = 4/9 At least one blue ball = 1-4/9 = 5/9 Quote Link to comment Share on other sites More sharing options...
manasi4gre Posted June 19, 2005 Share Posted June 19, 2005 agree with 5/9. Quote Link to comment Share on other sites More sharing options...
gre_gal Posted June 19, 2005 Share Posted June 19, 2005 i wanna know something.. What would the ans be if the question was say, There are 6 marbles in a bag. 2 are red, 2 blue and 2 green. Two marbles are drawn randomly without replacement. What the probability that atleast one of them is blue? Quote Link to comment Share on other sites More sharing options...
manasi4gre Posted June 19, 2005 Share Posted June 19, 2005 i wanna know something.. What would the ans be if the question was say, There are 6 marbles in a bag. 2 are red, 2 blue and 2 green. Two marbles are drawn randomly without replacement. What the probability that atleast one of them is blue? Probability of no blue= 4/6 * 3/5 = 2/5 Probability of atleast one blue= 1- 2/5 = 3/5 Quote Link to comment Share on other sites More sharing options...
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