SOLUTION: Walt made an extra $9000 last year from a part-time job. He invested part of the money at 5% and the rest at 6%. He made a total of $480 in interest. How much was invested at 6%?

Algebra ->  Customizable Word Problem Solvers  -> Finance -> SOLUTION: Walt made an extra $9000 last year from a part-time job. He invested part of the money at 5% and the rest at 6%. He made a total of $480 in interest. How much was invested at 6%?       Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 1144404: Walt made an extra $9000 last year from a part-time job. He invested part of the money at 5% and the rest at 6%. He made a total of $480 in interest. How much was invested at 6%?
Answer by greenestamps(13198) About Me  (Show Source):
You can put this solution on YOUR website!


(1) A traditional algebraic solution....

let x be the amount invested at 5%
then 9000-x is the amount invested at 6%

The total interest is 5% of x plus 6% of (9000-x):

.05%28x%29%2B.06%289000-x%29+=+480

Solve using basic algebra....

(2) A solution found by comparing the actual interest to the amounts of interest if the whole $9000 had been invested at one rate of the other....

$9000 all at 5% would yield $450 interest
$9000 all at 6% would yield $540 interest

$480 is 1/3 of the way from $450 to $540 (picture the three numbers 450, 480, and 540 on a number line...)

Therefore, 1/3 of the total was invested at the higher rate.

ANSWER: 1/3 of $9000, or $3000, at 6%; the other $6000 at 5%.

CHECK:
.05(6000)+.06(3000) = 300+180 = 480