SOLUTION: Kevin invests $5000 in one account and $8000 in an account paying 4% more in interest. He earned $1230 in interest after 1 year. What were the interest rates at which he invested h

Question 913937: Kevin invests $5000 in one account and $8000 in an account paying 4% more in interest. He earned $1230 in interest after 1 year. What were the interest rates at which he invested his money?
Answer by richwmiller(17219) (Show Source): You can put this solution on YOUR website!
We have both amts invested 5000 and 8000
we know the total interest earned 1230
We know the difference in rates is 4%
x*5000-y*8000=1230
x=y-0.04
substitute for x
(y-0.04)*5000+y*8000=1230
y*5000-0.04*5000+y*8000=1230
y*13000-200.0=1230
y*13000-200.0=1230
y*13000=1430.0
y=1430.0/13000
y=0.11
y=11.0% amt $8000
x=0.11-0.04
x=0.07
x=7.0% amt $5000
check
x*5000+y*8000=1230
0.07*5000+0.11*8000=1230
350.0+880.0=1230
1230.0=1230
ok
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