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Math Help - Word Problem

  1. #1
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    Word Problem

    A substance is 99% water. Some water evaporates, leaving a substance that is 98% water. How much of the water has evaporated?

    I am having a very difficult time setting up an algebraic equation to solve this problem. I honestly do not know where to begin. None of the work I have done on this problem is worth posting. Perhaps I am over-thinking this one...
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  2. #2
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    Re: Word Problem

    How much water did you start with?
    How much water left?
    How much water did you have left?

    Answer these questions and you nearly are done.
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  3. #3
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    Re: Word Problem

    Hi themathkid.
    Try this 100grams of a salt solution contains 1 gm 0f salt
    let x = water evaporated gms
    100-x = weight 0f remaining solution .What is the new conc of salt in terms of f(x)?
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  4. #4
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    Re: Word Problem

    Quote Originally Posted by bjhopper View Post
    Hi themathkid.
    Try this 100grams of a salt solution contains 1 gm 0f salt
    let x = water evaporated gms
    100-x = weight 0f remaining solution .What is the new conc of salt in terms of f(x)?
    f(x) = 1/(100-x)

    or

    f(x) = 1/(99-x)

    Does this mean that 50% of the water has evaporated?!?!?
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  5. #5
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    Re: Word Problem

    Hi the mathkid,
    After the x gms of water evaporate the salt weight does not change ( it is not volative)The desired salt concentration is 2% or .02 fraction so the equation is 1/100-x = .02
    x= 50 grams or 50% of the orginal solution
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