Question

Mona invests $1000 at 7% yearly interest. How much does she have to invest at 4% so that the total yearly interest from the two investments exceeds $138?

Answer 1

more than $1700

Explanation:

If P represents the amount invested at 4%, Mona's annual interest is ...

$1000×0.07 + P×0.04 > $138

P×0.04 > $68 . . . . . . subtract $70

P > $1700 . . . . . . . . . divide by the coefficient of P

Mona must invest more than $1700 at 4% to achieve total yearly interest of more than $138.