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Math Help - find and solve the equation- algebra

  1. #1
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    find and solve the equation- algebra

    The sum of Kris and Victor's ages is 27 years. In three years, Victor will be three times as old as Kris. What are their present ages?

    Find the solution using only one variable.
    Last edited by Splits; October 20th 2012 at 08:10 PM.
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: find and solve the equation- algebra

    Let K be Kris' age and V be Victor's age.

    The statement "The sum of Kris and Victor's ages is 27 years" becomes what equation?

    The statement "In three years, Victor will be three times as old as Kris" becomes what equation?

    Post what you think, and we will guide you from there,
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  3. #3
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    Re: find and solve the equation- algebra

    Thank you very much but I am not allowed to use two different variables. Do you know how i can do it with one variable?
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  4. #4
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    Re: find and solve the equation- algebra

    I'll try it your way though.
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  5. #5
    MHF Contributor MarkFL's Avatar
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    Re: find and solve the equation- algebra

    Well, you are given two unknowns and two statements which are essentially equations, so the easiest way is to use two variables, and the two statements to get a 2X2 linear system.

    Are you not studying systems of equations?
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  6. #6
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    Re: find and solve the equation- algebra

    "The sum of Kris and Victor's ages is 27 years"
    y+(27-y)=27
    "In three years, Victor will be three times as old as Kris" I got the 1st part i think, but i don't know what goes on the right side of the equation.
    27-y+3 (would be victor's age in three years) and y+3 (would be kris's age) but i don't know how to put them together.
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  7. #7
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    Re: find and solve the equation- algebra

    we are learning how to solve equations with one variable. So 27-y would be the second variable. We have not been using two variables in class, so I don't know if my teacher would be ok with me using more than one.
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  8. #8
    MHF Contributor MarkFL's Avatar
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    Re: find and solve the equation- algebra

    Okay, this seems an odd way to go about it, since if we write:

    K+V=27

    We find:

    K=27-V

    Now, for the second statement, I would write:

    V+3=3(K+3)

    Which gives us:

    V+3=3(27-V+3)=3(30-V)

    And now I would solve for V.
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  9. #9
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    Re: find and solve the equation- algebra

    Thank you very much for your help! I asked 5 other people and they couldn't do it.
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