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Math Help - Probability that at least 1 was selected

  1. #1
    Newbie sweetkendra's Avatar
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    Question Probability that at least 1 was selected

    Having a bit of trouble with this one: Any help will be appreciated.

    Suppose you are going to draw 2 jellyfish, without replacement, from a tank that contains 5 mushroom jellyfish and 3 cannonball jellyfish. Find the probability that at least 1 cannonball jellyfish will be selected.

    a. 5/15
    b. 9/14
    c. 15/28
    d. 1
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  2. #2
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    Quote Originally Posted by sweetkendra View Post
    Having a bit of trouble with this one: Any help will be appreciated.

    Suppose you are going to draw 2 jellyfish, without replacement, from a tank that contains 5 mushroom jellyfish and 3 cannonball jellyfish. Find the probability that at least 1 cannonball jellyfish will be selected.

    a. 5/15
    b. 9/14
    c. 15/28
    d. 1
    Pr(X \geq 1) = 1 - Pr(X = 0).

    Pr(X = 0) = \frac{{3 \choose 0} \times {5 \choose 2}}{{8 \choose 2}}, that is,

    (the number of ways of choosing zero cannonball AND two mushroom0/(the number of ways of choosing two fish from eight).
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  3. #3
    Newbie sweetkendra's Avatar
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    Many thanks

    Thank you for your help, I understand now.


    Quote Originally Posted by mr fantastic View Post
    Pr(X \geq 1) = 1 - Pr(X = 0).

    Pr(X = 0) = \frac{{3 \choose 0} \times {5 \choose 2}}{{8 \choose 2}}, that is,

    (the number of ways of choosing zero cannonball AND two mushroom0/(the number of ways of choosing two fish from eight).
    Follow Math Help Forum on Facebook and Google+

  4. #4
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    Quote Originally Posted by sweetkendra View Post
    Thank you for your help, I understand now.
    You're very welcome. Lovely manners
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