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%
