SOLUTION: You are going to invest $20, 000, part at 12% and part at 16%. What is the most that can be invested at 12% in order to make at least $3, 000 interest per year?

Question 799240: You are going to invest $20, 000, part at 12% and part at 16%. What is the most that can be invested at 12% in order to make at least $3, 000 interest per year?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Part I 16.00% per annum ------------- Amount invested =x
Part II 12.00% per annum ------------ Amount invested = y
20000
Interest----- 3000.00

Part I 16.00% per annum ---x
Part II 12.00% per annum ---y
Total investment
x + 1 y= 20000 -------------1
Interest on both investments
16.00% x + 12.00% y= 3000
Multiply by 100
16 x + 12 y= 300000.00 --------2
Multiply (1) by -16
we get
-16 x -16 y= -320000.00
Add this to (2)
0 x -4 y= -20000
divide by -4
y = 5000 - x)
Part I 16.00% $ 15000
Part II 12.00% $ 5000

CHECK
15000 --------- 16.00% ------- 2400.00
5000 ------------- 12.00% ------- 600.00
Total -------------------- 3000.00

m.ananth@hotmail.ca

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