How much did Jolene invest at each rate?

Question

Jolene invests her savings in two bank accounts, one paying 3 percent and the other paying 10 percent simple interest per year. She puts twice as much in the lower-yielding account because it is less risky. Her annual interest is 7632 dollars. How much did she invest at each rate?

Answer 1

.10x +(.03)2x=7,632

.16x=7632

x=7632/.16= $47,700 at 10%

2x= $95,400 at 3%

.1(47700)+ .03(95400)

=4770+2862

=7632

average interest rate = 5 1/3 % =7632/3(47700)

10-5 1/3= 4 2/3

5 1/3-3=2 1/3

4 2/3 = twice 2 1/3

twice as much invested at 3 as at 10%