Question

Eric took $7000 of his income last year and invested it, part at 7% and the rest at 9%. He earned $570 from investments. How much did he invest at each rate?

Answer 1

He invested 3,000 at 7% and 4,000 at 9%.

Explanation:

From the information given, you can write the following equations:

x+y=7,000 (1)

0.07x+0.09y=570 (2)

You can solve for x in (1)

x=7,000-y (3)

Now, you can replace (3) in (1) and solve for "y":

0.07(7,000-y)+0.09y=570

490-0.07y+0.09y=570

0.02y=80

y=80/0.02

y=4,000

Finally, you can replace the value of "y" in (3):

x=7,000-4,000

x=3,000

According to this, the answer is that he invested 3,000 at 7% and 4,000 at 9%.