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Brandon invested $20 000. He invested part of the money in a term deposit paying 4% annual interest,
three times as much in a government bond paying 5% annual interest, and the rest in a second mortgage
paying 7% annual interest. If he earned a total of $1130 interest in one year, how much did he invest at each rate?
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Invested x at 4%
3x at 5%
and (20000-4x) at 7%.
Write the total interest equation
0.04x + 0.05*(3x) + 0.07*(20000-4x) = 1130 dollars.
Simplify and find x
0.04x + 0.15x + 1400 - 0.28x = 1300
-0.09x = 1130-1400
0.09x = 270
x = 270/0.09 = 27000/9 = 3000.
ANSWER. $3000 invested at 4%; 3*3000 = 9000 dollars invested at 5%;
and the rest (20000-3000 - 9000) = 8000 dollars invested at 7%.
Solved.