SOLUTION: Walt made an extra $9000 last year from a part-time job. he invested part of the money at 9% and the rest at 8%. he made a total of $770 in interest. How much was invested at 8%

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 9% and the rest at 8%. he made a total of $770 in interest. How much was invested at 8%      Log On


   

Question 148933: Walt made an extra $9000 last year from a part-time job. he invested part of the money at 9% and the rest at 8%. he made a total of $770 in interest. How much was invested at 8%?
Found 2 solutions by checkley77, stanbon:
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
.09X+.08(9000-X)=770
.09X+720-.08X=770
.01X=770-720
.01X=50
X=50/.01
X=5,000 INVESTED @ 9%
9,000-5,000=4,000 INVESTED @ 8%.
PROOF:
.09*5000+.08*4000=770
450+320=770
770=770

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Walt made an extra $9000 last year from a part-time job. he invested part of the money at 9% and the rest at 8%. he made a total of $770 in interest. How much was invested at 8%?
--------------------------
Quantity Equation: x + y = 9000
Interest Equation: 0.09x + 0.08y = 770
--------------------------------------------
Modify the equations
9x + 9y = 81000
9x + 8y = 77000
-------------------
Subtract 2nd from 1st to get:
y = 4000 (Amt. invested at 8%)
Since x+y = 9000, x = 5000 (Amt. invested at 9%)
========================
Cheers,
Stan H.
=============================