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Convert 25 to 2.5? how?

  1. Oct 19, 2008 #1
    any formulas pls.
     
  2. jcsd
  3. Oct 19, 2008 #2

    rock.freak667

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    Homework Helper

    [tex]\frac{25}{10}=2.5[/tex]


    What exactly are you asking for?
     
  4. Oct 19, 2008 #3
    i need the formula in excel
    i need to convert 100 to 1.0, 99 to 1.1 so on

    to make it simple how do you convert 25 to 2.5?
     
  5. Oct 19, 2008 #4
    You need,

    www.mrexcel.com

    or similar. Try a google search on excel tutorials.
     
  6. Oct 19, 2008 #5
    divide by 10 :/

    25/10 = 2.5 :/ not sure if this is write, just thought i'd try to help
     
  7. Oct 20, 2008 #6

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    Divide by 10? You have not stated what you really want to do. There are an infinite number of ways to "convert 10 to 1.0, 99 to 1.1" that would give different results for all other numbers.

    A LINEAR function, the simplest, is of the form y= ax+ b. You want y= 1 when x= 100 and y= 1.1 when x= 99 so you want 1= 100a+b and 1.1= 99a+ b. Subtracting the first equation from the second, 0.1= -a so a= -0.1. Then the first equation becomes 1= -10+ b so b= 11.

    If y= -0.1x+ 11 then x= 100 gives y= -0.1(100)+ 11= -10+ 11= 1 and x= 99 gives y= -0.1(99)+ 11= -9.9+ 11= 1.1.

    However, if x= 25, y= -0.1(25)+ 11= -2.5+ 11= 8.5, not 2.5.

    If you really want to transform 100 to 1, 99 to 1.1, and 25 to 2.5, you will need at least a quadratic function: y= ax2+ bx+ c.

    Then 1= 10000a+ 10b+ c, 1.1= 9801a+ 99a+ c, and 2.5= 625a+ 25b+ c. Solve those equations for a, b, and c.

    However, I would suggest that you rethink what it is that you are trying to do.
     
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