SOLUTION: Joe invests $6000, part at 5% interest and the rest at 7%. If his annual interest income is $372, how much did he invest at each rate?

Question 820681: Joe invests $6000, part at 5% interest and the rest at 7%. If his annual interest income is $372, how much did he invest at each rate?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Part I 5.00% per annum ------------- Amount invested =x
Part II 7.00% per annum ------------ Amount invested = y
6000
Interest----- 372.00

Part I 5.00% per annum ---x
Part II 7.00% per annum ---y
Total investment
x + 1 y= 6000 -------------1
Interest on both investments
5.00% x + 7.00% y= 372
Multiply by 100
5 x + 7 y= 37200.00 --------2
Multiply (1) by -5
we get
-5 x -5 y= -30000.00
Add this to (2)
0 x 2 y= 7200
divide by 2
y = 3600
Part I 5.00% $ 2400
Part II 7.00% $ 3600

CHECK
2400 --------- 5.00% ------- 120.00
3600 ------------- 7.00% ------- 252.00
Total -------------------- 372.00

m.ananth@hotmail.ca

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