Mrs. Powell has $800 invested in stocks and $500 invested in a Certificate of Deposit. The CD has an interest rate twice as great as the stocks. If her annual interest on these two investments is $45, at what rate of interest is the $500 invested?
Let's use the variable "r" to represent the investment rate of the stocks: 2r(500) + r(800) = 45 1000r + 800r = 45 1800r = 45 r = 0.025 2r = 0.05 The $500 is invested at 5%
