SOLUTION: Walt made an extra $9000 last year from a part-time job. He invested part of the money at a 9% annual rate of interest, and the rest at 8% annual rate of interest. At the end of th

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: Walt made an extra $9000 last year from a part-time job. He invested part of the money at a 9% annual rate of interest, and the rest at 8% annual rate of interest. At the end of th      Log On


   

Question 477895: Walt made an extra $9000 last year from a part-time job. He invested part of the money at a 9% annual rate of interest, and the rest at 8% annual rate of interest. At the end of the year, he made a total of $770 in interest. How much was invested at 8%?
Answer by mangopeeler07(462) About Me  (Show Source):
You can put this solution on YOUR website!
9000=total money
Money at 9%=x
Money at 8%=9000-x (because it's the rest)

increase interest=770. so 9000+770= 9770.
So set up the equation:
1.09x%2B1.08%289000-x%29=9770 Because x+ 9% of x and (9000-x) + 8% of that equals 9770.
Simplify
1.09x%2B9720-1.08x=9770
Simplify again
.01x%2B9720=9770
Subtract 9720 from both sides.
.01x=50
Divide each side by .01
x=5000
Therefore:
$5000 was invested at 9%, and $4000 was invested at 8%.