Jack invests $1500 at a certain annual interest rate, and he invests another $3000 at an annual rate that is one-half percent higher. if he receives a total of $375 interest in 1 year, at what rate is the $1500 invested?

Let r be the rate which $1500 invested. thus r+0.005 is the rate which $3000 invested. then, 1500r + 3000 (r+0.005) = 375 1500r + 3000r + 15 = 375 4500r + 15 = 375 4500r = 375-15 4500r = 360 r = 4500/360 12.5 so, rate = 12.5%