Math
posted by Lisa on .
Betsy, a recent retiree, requires $6,000 per year in extra income. She has $60,000 to invest and can invest in Brated bonds paying 13% per year or in a certificate of deposit (CD) paying 3% per year. How much money should be invested in each to realize exactly $6,000 in interest per year?
The amount of money invested at 13%?
The amount of money invested at 3%?

Investments:
x dollars @ 13%,
y dollars @ 3%,
x + y = 60000,
0.13x + 0.03y = 6000,
Multiply the 1st Eq by 0.13:
0.13x  0.13y = 7800,
0.13x + 0.03y = 6000,
Add the 2 Eqs:
0.1y = 1800,
y = 18000,
Substitute 18000 for y in the 1st Eq:
x + 18000 = 60000,
x = 60000  18000 = 42000.
She invested:
$42000 @ 13%,
$18000 @ 3%.