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Math Help - Interest Calculation

  1. #1
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    Interest Calculation

    Not sure how to go about answering this homework question:

    You invested $11,000 in 2 accounts paying 4% and 8% annual interest. If the total interest earned for the year was $760, how much was invested at (a) 4% and (b) 8%?

    Thanks for the help!
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  2. #2
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    Quote Originally Posted by bearhug View Post
    Not sure how to go about answering this homework question:

    You invested $11,000 in 2 accounts paying 4% and 8% annual interest. If the total interest earned for the year was $760, how much was invested at (a) 4% and (b) 8%?

    Thanks for the help!
    Let n be the amount invested in the account with 4%. Therefore 11000-n is invested in the account with 8%

    I_{4\%}(1) = (0.04n)^1 = 0.04n

    I_{8\%}(1) = [(11000-n)(0.08)]^1 = 880-0.08n

    These totals are equal to $760. So we add them to give:

    880-0.08n+0.04n = 760

    Solve for n which will be the answer to part a. To find the answer to part b subtract the value of n from 11,000

    -0.04n = -120

    n = \$\,3000

    Therefore $3,000 is invested at 4% and $8,000 is invested at 8%

    I am not 100% sure about the position of n regarding the power. In this case it's not important for the power 1 doesn't change anything
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