Question 420200: jonathan invested a total of $3200, part at 4% simple interest and part at 5% simple interest. at the end of 1 year, the investments earned $145 interest. how much was invested at each rate?
Answer by mananth(16946)   (Show Source):
You can put this solution on YOUR website! 4.00% per annum------------- x
5.00% per annum------------ y
total investment 3200
Interest----- $145.00
....
x + y 3200 ------------------------1
4.00% x + 5.00% y = $145.00
Multiply by 100
4 x + 5 y = $14,500.00 --------2
Multiply (1) by -4
we get
-4 x -4 y = -12800
Add this to (2) we get
y = $1,700.00
y =$1,700.00 investment at 5.00%
Balance $1,500.00 investment at 4.00%
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