SOLUTION: 3. Walt made an extra $12,000 last year from a part-time job. He invested part of the money at 7% and the rest at 9%. He made a total of $970 in interest. How much was invested at

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: 3. Walt made an extra $12,000 last year from a part-time job. He invested part of the money at 7% and the rest at 9%. He made a total of $970 in interest. How much was invested at       Log On


   

Question 179560: 3. Walt made an extra $12,000 last year from a part-time job. He invested part of the money at 7% and the rest at 9%. He made a total of $970 in interest. How much was invested at 7%?

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
Let x = the amount Walt invested at 7%, so the remainder ($12000-x) was invested at 9%.
The interest earned on these two amounts can be expressed as:
(7%)(x) + (9%)($12000-x) and the sum of these two amounts is given as $970.00
Now you can write the equation that will allow you to so;ve for x, the amount invested at 7%.
First, change the percentages to their decimal equivalents:
(7% = 0.07) and (9% = 0.09)
0.07x%2B0.09%2812000-x%29+=+970 Simplifying this, you'll get:
0.07x%2B1080-0.09x=+970 Combine the x-terms.
-0.02x%2B1080+=+970 Subtract 1080 from both sides of the equation.
-0.02x+=+-110 Finally, divide both sides by -0.02
highlight%28x+=+5500%29
$5,500.00 was invested at 7% while $12000-$5500 = $6,500.00 was invested at 9%