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    this person has 20 ties

    2 red 3 blue 15 mixed colours
    he selects 2

    find the probability that at most one is red
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    trying to help a friend but i forgot the method :-s
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    (Original post by ihatePE)
    ...
    Hint: Does 1 - probability (of something) ring a bell for you?
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    (Original post by Zacken)
    Hint: Does 1 - probability (of something) ring a bell for you?
    it does but elaborate?

    1 - 2/20?? i tend to forget everything after exams :s
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    (Original post by ihatePE)
    it does but elaborate?

    1 - 2/20?? i tend to forget everything after exams :s
    Find the probability that they are both red. Then 1 - that is the probability that they are not both red, which is the same as saying that either none or one is red which is the same as saying that at most one is red.
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    (Original post by Zacken)
    Find the probability that they are both red. Then 1 - that is the probability that they are not both red, which is the same as saying that either none or one is red which is the same as saying that at most one is red.
    so 1 - 4/40?

    or 1 - 1/10?
    i feel so dumb
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    (Original post by ihatePE)
    so 1 - 4/40?

    or 1 - 1/10?
    i feel so dumb
    He has twenty ties. He picks two, the probability that the first one is red is 2/20. The probability that the second one is red is 1/19.

    The probability that he gets two reds is then 2/20 * 1/19.
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    (Original post by Zacken)
    He has twenty ties. He picks two, the probability that the first one is red is 2/20. The probability that the second one is red is 1/19.

    The probability that he gets two reds is then 2/20 * 1/19.
    so 1 - (2/20 * 1/19) ?

    does 2/20 * 1/19 make 2/380?

    then how would i take that from 1
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    (Original post by ihatePE)
    so 1 - (2/20 * 1/19) ?

    does 2/20 * 1/19 make 2/380?

    then how would i take that from 1
    Yeah, it does. What's 1 - \frac{1}{190}?
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    (Original post by Zacken)
    Yeah, it does. What's 1 - \frac{1}{190}?
    189/190?

    would i need to simplify?
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    im literally so freaked out at how stupid i am right now
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    (Original post by ihatePE)
    189/190?

    would i need to simplify?
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    im literally so freaked out at how stupid i am right now
    How could you simplify that?
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    (Original post by Zacken)
    How could you simplify that?
    i see :P
 
 
 
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