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Math 0098

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Last year, Joe had to invest. He invested some of it in an account that paid simple interest per year, and he invested the rest in an account that paid simple interest per year. After one year, he received a total of in interest. How much did he invest in each account?

  • Math 0098 - ,

    Do you have numbers for this problem?

  • Math 0098 - ,

    Last year, Joe had 10,000 to invest. He invested some of it in an account that paid 7% simple interest per year, and he invested the rest in an account that paid 9% simple interest per year. After one year, he received a total of $860 in interest. How much did he invest in each account?




    (sorry bout that).

  • Math 0098 - ,

    x = amount in the first account
    y = amount in the second account.

    total invested:

    x + y = 10,000

    since Interest = Principles times rate times time.

    .07x + .08y = 860

    Now, you work with those two equations.

    I would multiply the bottom equation by 100 to get rid of the decimals.

    x + y = 10000
    7x + 8y = 86000

    Now, you can solve this by using the substitution method or the addition method.

    I probably would use the addition(also known as the elimination method.)
    Multiply the top equation by -7 and solve for y. Once you have y, you can find x. Then be sure to check x and y in both equations.

  • Math 0098 - ,

    where did you get .08 from?

  • Math 0098 - ,

    Sorry.. the .08 is a typo. It should be .09

    Which makes the equation 7x + 9y = 86000

  • Math 0098 - ,

    it would be 7x+7y=70000? I don't know how to solve the two equations

  • Math 0098 - ,

    I don't think I'm doing this right because i am getting HUGE numbers like 156,000

  • Math 0098 - ,

    -7x -7y =70000
    7x + 9y =86000

    2y = 156000

    divide by 2 and you get 7800 for y
    so the other amount must be 2200.

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