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Math Help - Proportion

  1. #1
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    Proportion

    Hey, - I'm taking Geometry as a course, and since we've just done doing proportions, I think it's the most accurate forum to post my question, which I could not find by searching; - however, I stuck on a problem that confuses me everytime I have to look on the question, - a proportion that looks like this:

    Proportion-mathfraction.png

    I know that I need to cross multiply and all the good stuff, (I've been hearing this more than 2 times now), - i just need help on the steps doing it with the nice and cool n's.

    Regards
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  2. #2
    MHF Contributor
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    Quote Originally Posted by Cyloc View Post
    Hey, - I'm taking Geometry as a course, and since we've just done doing proportions, I think it's the most accurate forum to post my question, which I could not find by searching; - however, I stuck on a problem that confuses me everytime I have to look on the question, - a proportion that looks like this:

    Click image for larger version. 

Name:	mathfraction.png 
Views:	26 
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ID:	20109

    I know that I need to cross multiply and all the good stuff, (I've been hearing this more than 2 times now), - i just need help on the steps doing it with the nice and cool n's.

    Regards
    \displaystyle\frac{n-2}{2n}=\frac{n+4}{2n+5}\Rightarrow\ \left[\frac{2n+5}{2n+5}\right]\;\left[\frac{n-2}{2n}\right]=\left[\frac{2n}{2n}\right]\;\left[\frac{n+4}{2n+5}\right]

    \displaystyle\Rightarrow\frac{2n^2-4n+5n-10}{(2n+5)(2n)}=\frac{2n^2+8n}{(2n)(2n+5)}

    \displaystyle\ 2n^2+n-10=2n^2+8n\Rightarrow\ n-10=8n\Rightarrow\ 7n=-10
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