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Math Help - help please

  1. #1
    Member
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    help please

    Hi, could some one help with this please. if possible could you show me what the venn or tree diagram should look like.

    A cage holds two litres of rats. One litter comprises three females and four males, and the other comprises two females and six males. a random selection of two rats is made.

    i need to find as a fraction , the probability that the two rats are
    i) from the same litter
    ii) of the same sex
    iii)from the same litter and from same sex
    iiii)from the same litter given that they are of the same sex

    Thank you
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by Chez_ View Post
    Hi, could some one help with this please. if possible could you show me what the venn or tree diagram should look like.

    A cage holds two litres of rats. One litter comprises three females and four males, and the other comprises two females and six males. a random selection of two rats is made.

    i need to find as a fraction , the probability that the two rats are
    i) from the same litter[/tex]
    There are two mutualy exclusive cases here all from the first litter and all from the second litter.

    There are 7 rats in litter 1 and 8 rates in litter 2 for a total of 15.

    P(both from litter 1)=(7/15)(6/14)

    (that is the probability that the first rat selected is from litter 1 is 7/15 times
    the probability that the second rat selected (given that the first is from litter 1) is 6/14)

    P(both from litter 2)=(8/15)(7/15)

    P(both from same litter) = P(both from litter 1)+P(both from litter 2).

    RonL
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