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Math Help - Scale problem

  1. #1
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    Scale problem

    A copying machine reduces a 12" line segment to 10.5". At this setting, what would a 16" line segment become?
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    Quote Originally Posted by cherryperry View Post
    A copying machine reduces a 12" line segment to 10.5". At this setting, what would a 16" line segment become?
    I'm solving it like this:

    10.5 = n
    12 = 100

    10.5 x 100 divided by 12 = 87.5%

    So then I multiply 16 x .875 = 14. Is that right? Or is there another (better) way?
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  3. #3
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    Quote Originally Posted by cherryperry View Post
    I'm solving it like this:

    10.5 = n
    12 = 100

    10.5 x 100 divided by 12 = 87.5%

    So then I multiply 16 x .875 = 14. Is that right? Or is there another (better) way?
    cherryperry: You are correct. If copier is reducing 16 in. down to 10.5 in., then it is reducing 87.5%. So, 87.5% of 16 in. = 14 in. 10.5 in. divided by 16 = .875. 16 x .875 = 14
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  4. #4
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    Quote Originally Posted by cherryperry View Post
    A copying machine reduces a 12" line segment to 10.5". At this setting, what would a 16" line segment become?
    12k = 10.5

    k = \frac{10.5}{12}

     = \frac{105}{120}

     = \frac{7}{8}.



    So at the same setting...

    16k = 16\left(\frac{7}{8}\right)

     = 14.


    Therefore, this setting will reduce a 16'' segment to 14''.
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  5. #5
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    Quote Originally Posted by cherryperry View Post
    A copying machine reduces a 12" line segment to 10.5". At this setting, what would a 16" line segment become?
    cherryperry: One more time. . .

    Depending on how you daugther thinks, there is another way to see this problem. What the question (or ones like it) is asking is for a comparision between two ratios that are equal, one of them known and the other one unknown. So, the problem could be thought of as

    \left(\frac{x}{16}\right)=\left(\frac{10.5}{12}\ri  ght)

    Now, make the equality an equation equal to 0 --

    \left(\frac{x}{16}-\frac{10.5}{12}\right)=0

    Then "cross multiply" so that --

    {12}{x}={168}

    {x}={168} divided by  {12}={14}

    Here is another examlple --

    A 90 gal. container is filled with 22.5 gal. of fluid. How much fluid must be put into a 150 gal. container so that the percentage of fluid in both is equal?

    \left(\frac{x}{150}\right)=\left(\frac{22.5}{90}\r  ight)

    {90}{x}={3375}

    {x}={3375} divided by {90}={37.5}

    Also, a tip (which you may or may not already know): If you want to print a thread so that your daughter can review, if you click on the "Thread Tools" button it will show, among other things, "Printable Version." If you click on that it will print just the "meat" of the posts, without the advertising in between them.
    Last edited by DeanSchlarbaum; May 31st 2010 at 10:18 AM.
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