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Math Help - elementar probability question

  1. #1
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    elementar probability question

    I need help with this question:

    A student is writing a multiple choice quiz consisting of three questions, each having four choices and one correct answer each.

    (a)what is the chance that the student will get a perfect score by guessing?

    I think this should be \frac{1}{4}*\frac{1}{4}*\frac{1}{4}=\frac{1}{64}

    (b) what is the change that the student will get at least one question correct by guessing

    I'm not sure how to tackle this part. How do I calculate at least one right answer?
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: elementar probability question

    a) I agree.

    b) It is certain that the student will either get no questions correct (event X), or will get at least 1 correct (event Y), so we may state:

    P(X)+P(Y)=1

    P(Y)=1-P(X)

    Now, compute P(X) and then plug it into the above equation.
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  3. #3
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    Re: elementar probability question

    so P(X)= 3/4 * 3/4 * 3/4 = 27/64

    and therefore P(Y)=1-(27/64) = 37/64
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  4. #4
    MHF Contributor MarkFL's Avatar
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    Re: elementar probability question

    Yes, good work!
    Thanks from kingsolomonsgrave
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