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Math Help - the Phone problem

  1. #1
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    the Phone problem

    The probability of a girl getting a line busy every time when she calls is 1/3 and if she makes one call on each of 4 consecutive days, then

    A: Probability of getting the line busy on each of the 4 days
    B: 1/4
    C: A and B are equal
    D: It's not possible to answer

    [My Solution]

    Since each days is a separate Possible Outcome which is 1/3 and she calls one time each day, then on each of the days the probability that she gets the line busy is 1/3

    Is that true? Thank you
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  2. #2
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    Quote Originally Posted by Narek View Post
    The probability of a girl getting a line busy every time when she calls is 1/3 and if she makes one call on each of 4 consecutive days, then

    A: Probability of getting the line busy on each of the 4 days
    B: 1/4
    C: A and B are equal
    D: It's not possible to answer

    [My Solution]

    Since each days is a separate Possible Outcome which is 1/3 and she calls one time each day, then on each of the days the probability that she gets the line busy is 1/3

    Is that true? Thank you
    I guess the question is really asking for the probability that she gets 4 busy signals in a row
    over the 4 days if she makes 1 attempt per day.
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  3. #3
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    maybe you are right but as far as I understand it says : "if she makes one call on each of 4 consecutive days" then it seems to me like the questions asks for each of the possible outcomes of each day ... what do you think?
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  4. #4
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    Quote Originally Posted by Narek View Post
    maybe you are right but as far as I understand it says : "if she makes one call on each of 4 consecutive days" then it seems to me like the questions asks for each of the possible outcomes of each day ... what do you think?
    Yes, often the wording of the question is a little ambiguous
    when it comes to probabilities.

    Each day she has a 1/3 chance of getting a busy signal.

    Also, can you double-check the entire question as A should have a choice rather than the statement given.
    I would interpret the question (which is placed in the A option position (!)) as "all four days",
    in which case you'd use a "power of 4".

    Then again, the question may be asking for the seperate probabilities on each day,
    which is the answer you've given (!)
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