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-   -   Algebra signed fractions (https://www.askmehelpdesk.com/showthread.php?t=408744)

  • Oct 22, 2009, 03:57 PM
    Kaykay09
    Algebra signed fractions
    Okay so just starting algebra this year, and came upon the question: x + 4/7 = 3/8

    and the answer is - 11/56... where did the negative come from? And why is it negative and not posotive? Please help!! And remember I'm only starting algebra please explain in simplest terms possible
  • Oct 22, 2009, 04:01 PM
    Sprung09

    Try thinking about it knowing what relation the 56 has with the 7 and 8? Then think about creating common denominators for all the fractions from there? Let me know if this gets you anywhere.
  • Oct 22, 2009, 04:11 PM
    Kaykay09

    I am able to find the answer OK, I just don't understand why it is a -(negative)... I don't see where the - sign fit in...
  • Oct 22, 2009, 04:14 PM
    Sprung09
    Quote:

    Originally Posted by Kaykay09 View Post
    I am able to find the answer ok, I just don't understand why it is a -(negative)... I don't see where the - sign fit in....

    The answer fraction would be negative because when you change all the fractions to common denominators it would make the 4 and 3 greater than they are now. Making the fractions that they give you in the equation would creater greater fractions than the -11/56? Does this help at all?
  • Oct 22, 2009, 07:39 PM
    KISS

    x= 3/8 - 5/7 ; rewriting

    5/7 = ~.0.57
    ... (use Google as a calculator - just type 5/7 in the Google search bar)
    3/8= 0.375

    X ~= 0.375 - 0.57 ;3/8 is smaller than 5/7

    Now do you see where the negative sign comes from

    PS: That isn't the way to do the problem because of the aproximations.
  • Oct 22, 2009, 07:43 PM
    KISS
    Hey, I have to own up to my reputation once and a while. You can't readily tell if one is bigger than the other one at this stage in development.
  • Oct 24, 2009, 01:26 PM
    Kaykay09

    Wow! Thanks guys! Yeah those answers totally helped me out a lot... I get it now... since 3/8 is smaller than 4/7 that means that it would be a negative... gracias!
  • Oct 24, 2009, 01:39 PM
    KISS

    You can easily tell that when the common denominator is 8 * 7 or 56

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