Question

Amanda invested a total of $3,600 into three separate accounts that pay 5%, 7%, and 9% annual interest. Amanda has four times as much invested in the account that pays 9% as she does in the account that pays 5%. If the total interest for the year is $282, how much did Amanda invest in each account?

Answer 1

let x be the amount at 5%
4x at 9%
3600-(x+4x) at 7%

.05x + .09*4x + .07(3600-5x) = 282
.05x + .36x + 252 - .35x = 282
.06x = 30
x = 500

so, she has

500 at 5%
2000 at 9%
1100 at 7%