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Math Help - Is it logical???

  1. #1
    Junior Member
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    Unhappy Is it logical???

    Our math teacher said that cross multiplication method is not a logical method to solve in!!! even if the answer is right!!!
    so is he right?
    Last edited by lebanon; November 7th 2009 at 05:24 AM.
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  2. #2
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    If you are referring to the property in algebra that \frac{a}{b}=\frac{c}{d} implies ad=bc provided of course b,d are nonzero... then yes, this is a valid and completely sound property of real numbers.

    Perhaps what your professor means by "illogical" is that cross-multiplication is not a fundamental property or operation in algebra. The correct and logical step is to multiply both sides of the equation by bd. The term "cross multiply" is not so much a mathematical tool as it is a teaching tool, to help young (particularly math-hating) students remember how to proceed when faced with this type of problem.
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  3. #3
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    Thanks very much, because I was really confused
    Last edited by Jhevon; November 8th 2009 at 10:21 PM.
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