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Math Help - Word Problem Using Cramer's Rule

  1. #1
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    Word Problem Using Cramer's Rule

    Hi folks,
    My instructor has given us an extra credit sheet and it has this word problem that must be solved using cramer's rule. I know how to apply or solve using cramer's rule but I can't seem to properly create a system of equations. Maybe you guys could help me.

    Jenny receives $1,270 per year from three different investments totaling $20,000. One of the investments pays 6%, the second one pays 8%, and the third one pays 5%. If the money invested at 8% is $1,500 less than the amount invested at 5%, how much money has jenny invested in the investment that pays 6%?
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  2. #2
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    Quote Originally Posted by chipman316 View Post
    Hi folks,
    My instructor has given us an extra credit sheet and it has this word problem that must be solved using cramer's rule. I know how to apply or solve using cramer's rule but I can't seem to properly create a system of equations. Maybe you guys could help me.

    Jenny receives $1,270 per year from three different investments totaling $20,000. One of the investments pays 6%, the second one pays 8%, and the third one pays 5%. If the money invested at 8% is $1,500 less than the amount invested at 5%, how much money has jenny invested in the investment that pays 6%?
    Hi chipman36,

    This is how it shapes up to me:

    Let x = amount invested at 6%
    Let y = amount invested at 8%
    Let z = amount invested at 5%

    Total amount used to invest = 20000:
    [1] x+y+z=20000

    Annual return on investments:
    [2] .06x+.08y+.05z=1270

    Amount invested at 8% is $1,500 less than the amount invested at 5%
    [3] y=z-1500
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  3. #3
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    Thank you so much. The last system was really throwing me off. Simple subtraction I know but I somehow kept trying several different things only to get negative investment numbers. Thanks again!
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