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Homework Help: Quick question with matrices

  1. Feb 10, 2005 #1
    ok here is the question

    The annual interest on Sid Carrington's three investments amounted to $21300: 5% ona savings account, 9% on mutual funds, and 11% on bonds.If the amount of Sid's investment in bonds was triple the amount of his investment in the savings account, and the interest earned from his investment in bonds was equal to the dividends he received from his investment in mutual funds, find how much money he placed in each type of investment.

    ? $ in a savings account
    ? $ in mutual funds
    ? $ in bonds

    I set up the matrix as

    .05 .09 .11 21300
    3 0 -1 0
    0 1 -1 0

    and when I do rref on it I keep getting the wrong answer

    would be great if I could get some help on this within 45 minutes

  2. jcsd
  3. Feb 11, 2005 #2
    Your last line is wrong. The mutual fund investment is not equal to the bond investment. It's the income earned on each of them that is equal.
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