SOLUTION: Janet invested $27,000, part at 15% and part at 9%. If the total interest at the end of the year is $3,390, how much did she invest at 15%?

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: Janet invested $27,000, part at 15% and part at 9%. If the total interest at the end of the year is $3,390, how much did she invest at 15%?       Log On


   

Question 258029: Janet invested $27,000, part at 15% and part at 9%. If the total interest at the end of the year is $3,390, how much did she invest at 15%?
Answer by drk(1908) About Me  (Show Source):
You can put this solution on YOUR website!
This question is modeled after the I = prt question. IN this case however, we have two investments. So we can write
I = prt + prt
based on the given information, we get
(i) 3390+=+x%28.15%29%281%29+%2B+%2827000-x%29%28.09%29%281%29
simplifying (i) , we get
(ii) 3390+=+.15x+%2B+2430+-.09x
and then
(iii) 3390+=+.06x+%2B+2430
subtracting, we get
(iv) 1060+=+.06x
and dividing, we get
x = $11,777.78 @ 15%
and
27000 - x = $15,222.22 @ 9%.