SOLUTION: Susan invests 2 times as much money at 5% as she does at 4%. If her total interest after 1 year is $840, how much does she have invested at each rate?

Question 663056: Susan invests 2 times as much money at 5% as she does at 4%. If her total interest after 1 year is $840, how much does she have invested at each rate?
Answer by ReadingBoosters(3246) (Show Source): You can put this solution on YOUR website!
x = $ at 5%
y = $ at 4%
y = 2x
.05x + .04y = 840
.05x + .04(2x) = 840
.05x + .08x = 840
.13x = 840
x = $6,461.54 at 5%
y = 2(6461.54) = $12,923.08 at 4%
Proof
.05(6461.54) + .04(12923.08) =
323.08 + 516.92 = 840
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