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Math Help - salt solution problem

  1. #1
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    salt solution problem

    How many gallons of water must be mixed with 5 gal of 20% salt solution to make a 16% salt solution?

    I put 5 over x and .2 over .16 and came up with 1.25 gal, which is the correct answer. I need to know if this is the correct way to work the problem so that I can use it later.
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  2. #2
    Bar0n janvdl's Avatar
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    Quote Originally Posted by tigersblood View Post
    How many gallons of water must be mixed with 5 gal of 20% salt solution to make a 16% salt solution?

    I put 5 over x and .2 over .16 and came up with 1.25 gal, which is the correct answer. I need to know if this is the correct way to work the problem so that I can use it later.
    Shouldn't it be 5 gal + 1,25 gal?

    I may have misunderstood you, but the total should be 6,25 gal i think.
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  3. #3
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    Yes, the total is 6.25, but the question asks how much you should add. I've got the answer, I just need to know if I have the work correct. Should I cross multiply?
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  4. #4
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    Hello, tigersblood!

    How many gallons of water must be mixed with 5 gal of 20% salt solution
    to make a 16% salt solution?
    I would equate the amounts of water in the mixture.


    We have 5 gallons of solution which is 80% water: . 4 gallons of water.
    . . We will add x gallons of water.
    The mixture will contain: . x + 4 gallons of water.


    The mixture will be x+4 gallons of solution which is 84% water.
    . . It has: . 0.84(x + 4) gallons of water.


    We just expressed the final amount of water in two ways.

    . . There is our equation! . . . . x + 4 \:=\:0.84(x + 4)

    Now solve for x.

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