SOLUTION: Alfredo deposited $12000 in two accounts whose annual simple interest rates were 9% and 11%. How much did he deposit in each account if the interest earned by each was the same?

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Question 903357: Alfredo deposited $12000 in two accounts whose annual simple interest rates were 9% and 11%. How much did he deposit in each account if the interest earned by each was the same?
Found 2 solutions by Math_Boss, richwmiller:
Answer by Math_Boss(45) About Me  (Show Source):
You can put this solution on YOUR website!
x%2By=12000
0.09%2Ax=0.11%2Ay
x=12000-y
0.09%2A%2812000-y%29=0.11%2Ay
1080-0.09%2Ay=0.11%2Ay
1080=0.11%2Ay%2B0.09%2Ay
1080=0.2%2Ay
y=5400
x=12000-5400
x=6600
Ans:$6600 and $5400

Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
x+y=12000,
.09x=.11y
x=6600., y=5400.We know the total amount of money invested. $12000
x+y=12000,
We know that the difference in the two accounts is $0
0.09*x-0.11*y=0
x=12000-y
We substitute for x
0.09*(12000-y)-0.11*y=0
We multiply out
1080-0.09y-0.11*y=0
We combine like terms.
1080=0.2*y
Isolate y
y=5400 at 11%
Calculate x
x=12000-5400
x=6600 at 9%
We check
0.09*6600-0.11*5400=0
594-594=0
0=0
Since this statement is TRUE and neither amount is negative then it is ok