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Math Help - scale?

  1. #1
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    scale?

    I need help with some math.


    I need to turn 4 to 20 into a scale of 0 to 5


    example:


    I need math to turn this:

    4 = 0 pounds

    12 = 500 pounds

    20 = 1000 pounds


    into this:
    0 = 0 pounds

    2.5 = 500 pounds

    5 = 1000 pounds


    so it is scaled.

    can it be done?
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  2. #2
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    x\mapsto \frac5{16}(x-4)?
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  3. #3
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    could you explain your formula a little
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  4. #4
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    First I shifted the back by 4, so that the interval 4 to 20 becomes the interval 0 to 16. Then I scaled by 5/16 so that the interval 0 to 16 becomes the interval 0 to 5. Is that what you want?
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  5. #5
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    first of all, thanks for your help!

    I am not sure. I will do some checking and get back to you.
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  6. #6
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    Quote Originally Posted by maddas View Post
    First I shifted the back by 4, so that the interval 4 to 20 becomes the interval 0 to 16. Then I scaled by 5/16 so that the interval 0 to 16 becomes the interval 0 to 5. Is that what you want?

    lets say that i have 2 scroll bars, the one on the left scrolls between
    4 & 20 with 1/10 increments. when I scroll this scroll bar to 12 the scroll bar on the right displays 2.5


    so, if the left scroll bar was set to 1.1, what would the scroll bar on the right show??


    I hope this explains it better.
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  7. #7
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    If the left scroll bar scrolls between 4 and 20 how can it be set to 1.1? The formula I gave works for 12 ( \frac5{16}(12-4) = 5/2 = 2.5)...
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  8. #8
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    Quote Originally Posted by maddas View Post
    If the left scroll bar scrolls between 4 and 20 how can it be set to 1.1? The formula I gave works for 12 ( \frac5{16}(12-4) = 5/2 = 2.5)...

    sorry, i should have said: 5.1 for the left scroll bar.
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  9. #9
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    Quote Originally Posted by maddas View Post
    If the left scroll bar scrolls between 4 and 20 how can it be set to 1.1? The formula I gave works for 12 ( \frac5{16}(12-4) = 5/2 = 2.5)...
    sorry, I am at a loss to understand your answer
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  10. #10
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    Sorry. Suppose the left scroll bar is at position x. Then I think the right scroll bar will be at position \frac5{16}(x-4).
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  11. #11
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    does your formula mean:


    5/16 TIMES (x-4)
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  12. #12
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    Yes, what did you think it meant?
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  13. #13
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    I just wanted to make sure.
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  14. #14
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    how do I turn 15/16 into a decimal?
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