Mathematics
posted by Kevin on .
Carletta has $10,000 to invest. As her financial consultant you recommend that she invest in Treasury Bills that yield 6%, Treasury Bonds that yield 7%, and coroporate bonds that yield 8%. Carletta wants to have an annual income of $680, and the amount invested in corporate bonds must be half that invested in Treasury Bills. Find the amound she should place in each investment using matrix.

why use a matrix for such a simple question?
let the amount invested at corporate bonds be $x
then the amount invested in treasurey bonds is $2x
then the amount invested in treasure bills is 10000x2x
then .06(100003x) + .07(2x) + .08x = 680
solve for x