Solve the problem.
-Walt made an extra $\$ 9000$ last year from a part-time job. He invested part of the money at $8 \%$ and the rest at $7 \%$. He made a total of $\$ 680$ in interest. How much did he invest at each rate?
A) $\$ 5000$ at $7 \% ; \$ 4000$ at $8 \%$
B) $\$ 4000$ at $7 \% ; \$ 5000$ at $8 \%$
C) $\$ 4500$ at $7 \% ; \$ 5000$ at $8 \%$
D) $\$ 4000$ at $7 \%$; $\$ 7000$ at $8 \%$

Question

Quizplus · Accepted Answer

Let $x$ be the amount invested at $7\%$, then $9000 - x$ is the amount invested at $8\%$. The equation for the total interest is $0.07x + 0.08(9000 - x) = 680$. Solving this equation gives $x = 4000$, so Walt invested $\$4000$ at $7\%$ and $\$5000$ ($9000 - 4000$) at $8\%$.

Solve the Problem $9000\$ 9000$9000 Last Year from a Part-Time Job 8%8 \%8%

Solve the Problem $\$ 9000$ Last Year from a Part-Time Job $8 \%$