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Math Help - number of ways an item can be defective

  1. #1
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    number of ways an item can be defective

    I have the question
    There are 12 ways in which Manufactured item can be a minor defective and 10 ways in which it can be a major defective. In how many ways can 2 major and 2 minor defects occur?
    I would of thought to use 12P2 x 10P2 but that gives the completely the wrong answer
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  2. #2
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    Quote Originally Posted by renlok View Post
    I would of thought to use 12P2 x 10P2 but that gives the completely the wrong answer
    Use combinations and not permutations.
    _{12}\mathcal{C}_2=\frac{12\cdot 11}{2}
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