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Math Help - Need help with Percentage Word Problems.

  1. #1
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    Need help with Percentage Word Problems.

    There are two word problems that are giving me alot of trouble for an assignment that I have to do.

    A 50% saline solution mixed together with a 30% saline solution to get 30L of a 46% concentrated saline solution. How many litres of each are needed to be mixed?

    You invest a total of $1800 into two diffrent investments. One investment returned 9% and the other returned 6%. If the interest on the 9% was $102 more of a return than the return of the 6% investment then how much of your $1800 was in each seperate account?

    I don't know how to set up any of these problems. If I could have help with the set up I could do it. These are the only problems on the sheet giving me problems. Thanks for your assistance.
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  2. #2
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    Quote Originally Posted by (?)G View Post

    You invest a total of $1800 into two diffrent investments. One investment returned 9% and the other returned 6%. If the interest on the 9% was $102 more of a return than the return of the 6% investment then how much of your $1800 was in each seperate account?
    Let A be the amount of the first investment

    Let B be the amount of the second investment

    Quote Originally Posted by (?)G View Post

    You invest a total of $1800 into two diffrent investments.
     A+B = 1800

    Quote Originally Posted by (?)G View Post

    If the interest on the 9% was $102 more of a return than the return of the 6% investment then how much of your $1800 was in each seperate account?
     1.09A = 102 +1.06B

    Can you solve this system?

     A+B = 1800

     1.09A = 102 +1.06B
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  3. #3
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    Thanks, I knew the A+B= $1800 part, but the other part really threw me, with the one returned 9 percent was $102 more of a return than the 6 percent investment.

    So You have the 1.09, The 1 represents 100 percent, plus an extra 9 percent on top of one and 6 percent on top of the other?

    What about the saline solution one, I can't even make heads or tails of even the first equation.

    Here is my work just in case it can help somebody else out:

    A= -B+ 1800

    1.09( -B + 1800) = $102 + 1.06B "Equal Quantities Method"

    1860 = 2.15B

    1860/2.15 = 2.15B/2.15B

    (($865.12 = B))

    1.09A = 102 + 1.06 (865.12)

    1.09A = 102 + 917.03

    1.09A/1.09A = 1019.03/1.09

    (($934.89= A))

    When you add A and B up it is $1800.01, With rounding off certain numbers it is .01 over the $1800, but it's around the same area.
    Last edited by (?)G; October 13th 2009 at 05:58 PM. Reason: Adding Work
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  4. #4
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    Quote Originally Posted by (?)G View Post

    A 50% saline solution mixed together with a 30% saline solution to get 30L of a 46% concentrated saline solution. How many litres of each are needed to be mixed?
    I'm thinking to tackle this one similar to that of the second question

    A and B are the volumes of the 2 mixtures.

     50\%\times A + 30\%\times B = 46\%\times (A+B)

     A+B= 30

    can you finish it?
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  5. #5
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    Quote Originally Posted by pickslides View Post
    I'm thinking to tackle this one similar to that of the second question

    A and B are the volumes of the 2 mixtures.

     50\%\times A + 30\%\times B = 46\%\times (A+B)

     A+B= 30

    can you finish it?
    Was I right for the last one, by the way?
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  6. #6
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    Looks good.
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