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Math Help - Please help

  1. #1
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    Question Please help

    I need help with this problem .


    15 divide 6 2/3 =?

    A) 100 1/4 B) 2 1/4 C)100 D) 2 3/4

    I'm thinking the letter D
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  2. #2
    MHF Contributor Quick's Avatar
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    Quote Originally Posted by Angel King
    I need help with this problem .


    15 divide 6 2/3 =?

    A) 100 1/4 B) 2 1/4 C)100 D) 2 3/4

    I'm thinking the letter D
    You know: 15=\frac{15}{1} and 6\frac{2}{3}=\frac{20}{3}

    therefore we have equation: \frac{15}{1}\div \frac{20}{3}

    when dividing by a fraction you multiply by the reciprocal of the fraction, so we get: \frac{15}{1}\div \frac{20}{3}=\frac{15}{1}\times \frac{3}{20}=\frac{15\times3}{1\times20}=\frac{45}  {20}=2\frac{5}{20}=2\frac{1}{4}

    so the answer is B, not d

    BTW When I was taught to divide fractions my teachers would say that you would "cross multiply" so you can think of it like this:

    \frac{15}{1}\div\frac{20}{3}=\frac{15}{1}<br />
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\frac{20}{3}=\frac{15\times3}{1\times20}=\frac{45}  {20}

    did this post help?
    Last edited by Quick; August 24th 2006 at 10:12 AM.
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