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Math Help - false position

  1. #1
    Junior Member
    Joined
    Sep 2008
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    44

    false position

    Hello everyone,

    Could someone please explain to me how to do false position?

    For example, "a quantity; its half and its third are added to it. It becomes 10. What is the quantity?"

    My attempt:

    The algebraic way:
    x+1/2x+1/3x=10
    x=10/1+1/2+1/3
    x=60/11

    False position:

    Assume x=2

    2+1/2(2)+1/3(2)=
    11/3

    we want 12, so 12/11/3=36/11

    (answer)(guess)=2(36/11)=72/11

    Does anyone see where I went wrong? It should be 60/11, not 72/11. Does anyone know of an easy way of choosing the x value?

    Thank you very much
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  2. #2
    Super Member Deadstar's Avatar
    Joined
    Oct 2007
    Posts
    722
    Right ill try this one...
    I think you're supposed to pick x so that the fractions go.

    In this case try x=6.

    You get 6 + 3 + 2 = 11 which is not the right answer.

    But if we multiply 11 by 10/11 we get the right answer so multiply 6 by 10/11 and we do indeed get 60/11 as you said.

    Following your way... Pick x=2.

    Then you get 2 + 1 + 2/3 = 11/3 which is not the right answer but if we multiply it by 10*(3/11) we get the right answer so again multiply your x value by this to get 2*10*(3/11) to get 60/11 as required.
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  3. #3
    Member
    Joined
    Jan 2009
    Posts
    108
    " we want 12"

    no, we don't. that's where the problem was.
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