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Homework Help: Probability (Statistics)

  1. May 18, 2009 #1
    1. The problem statement, all variables and given/known data
    The security passes for a certain company are coloured yellow or white, they're provided with either a clip or a chain. The probability that a pass has a clip is 6/10, 2/3 of the white passes and 4/7 of the yellow ones are fitted with clips. A member of the company is stopped on his way into work find the probability that;

    The pass is yellow
    The pass is yellow with a chain

    If two people are stopped randomly as they enter find the probability that one pass will be yellow and the other white, and one will have a clip and the other a chain.
    2. Relevant equations


    3. The attempt at a solution

    Really frustrating question, is this question possible? :/ This is what i've tried, but it's wrong according to the book;

    (3/7 * 4/10) + (4/7 * 6/10) = 0.514 (I know this is wrong but I was trying anything)

    I just don't see how this is possible because surely it's dependant on the actual number that are white and yellow? Surely if there's 1000 white, and 5 yellow, the probability of a yellow is much different than with different numbers there, and they tell you no-where what to assume...

    Any help would be great.
  2. jcsd
  3. May 18, 2009 #2
    Got it, sorry, i always post too early.
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