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Thread: Probability Concepts

  1. #1
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    Probability Concepts

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    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 ?

  2. #2
    ..TM Bhakt.. 800ForSure's Avatar
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    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
    "GOOD LUCK"...for ur GMAT.

  3. #3
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    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?

  4. #4
    An Urch Guru Pundit Swami Sage
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    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

  5. #5
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    I agree with you, but somebody was saying it to be 8/9.

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    An Urch Guru Pundit Swami Sage
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    Nope : 1 - 4/9 = 5/9.
    RD

  7. #7
    ..TM Bhakt.. 800ForSure's Avatar
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    No Blue at all = 4/6 * 4/6 = 4/9

    At least one blue ball = 1-4/9 = 5/9
    "GOOD LUCK"...for ur GMAT.

  8. #8
    An Urch Guru Pundit Swami Sage manasi4gre's Avatar
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    agree with 5/9.

    "Fear less,hope more; whine less,breathe more;
    Talk less,work more; hate less,love more;
    Then all the good things are yours ."

    ---Proverb---

  9. #9
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    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?


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    An Urch Guru Pundit Swami Sage manasi4gre's Avatar
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    Quote Originally Posted by gre_gal
    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

    "Fear less,hope more; whine less,breathe more;
    Talk less,work more; hate less,love more;
    Then all the good things are yours ."

    ---Proverb---

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