Question

Phyllis invested 70000 dollars, a portion earning a simple interest rate of 4 percent per year and the rest earning a rate of 7 percent per year. After one year the total interest earned on these investments was 3910 dollars. How much money did she invest at each rate? At rate 4 percent? At rate 7 percent?

Answer 1

simpel interest, 70,000$, 1 yeer... sum at 4% & sum at 7%... interest=3,910$ so 0.04x +0.07*(70,000-x)=3,910$... 0.04x -0.07x +4,900=3,910$... -0.03x=3,910-4,900=-990$... x=990/0.03=33,000$(4%), so other part=70,000-33,000=37,000$ (7%)