SOLUTION: Melinda invested three times as much money at 9% yearly interest as she did at 7%. Her total yearly interest from the two investments was $170. How much did she invest at each ra

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Question 691115: Melinda invested three times as much money at 9% yearly interest as she did at 7%. Her total yearly interest from the two investments was $170. How much did she invest at each rate?
I only set up this
9(.09x)+ .07x= 170
Answer by stanbon(75887) About Me  (Show Source):
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Melinda invested three times as much money at 9% yearly interest as she did at 7%. Her total yearly interest from the two investments was $170. How much did she invest at each rate?
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Quantity Equation: n = 3s
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Interest Eqution:: 0.09n + 0.07s = 170
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Substitute for "n" and solve for "s"
0.09(3s) + 0.07s = 170
Multiply thru by 100 to get:
27s + 7s = 17000
34s = 17000
s = $500.00 (amt. invested at 7%)
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solve for "n" using n = 3s
n = $1500 (amt. invested at 9%)
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Cheers,
stan H.
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