SOLUTION: Isabel invested $8000 dollars, part at 9% per annum and the remainder at 4% per annum. After one year, the total interest from these investments was $420. How much did she invest a

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: Isabel invested $8000 dollars, part at 9% per annum and the remainder at 4% per annum. After one year, the total interest from these investments was $420. How much did she invest a      Log On


   

Question 218369: Isabel invested $8000 dollars, part at 9% per annum and the remainder at 4% per annum. After one year, the total interest from these investments was $420. How much did she invest at each rate?
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
.09X+.04(8,000-X)=420
.09X+320-.04X=420
.05X=420-320
.05X=100
X=100/.05
X=2,000 AMOUNT INVESTED @ 9%.
8,000-2,000=6,000 AMOUNT INVESTED @ 4%.
PROOF:
.09*2,000+.04*6,000=4200
180+240=420
420=420