SOLUTION: Peter and Shelly invested $10,000 for one year. Part of it was invested at 10% simple interest and the rest was invested at 6%. At the end of year the couple had earned exactly $86

Question 800979: Peter and Shelly invested $10,000 for one year. Part of it was invested at 10% simple interest and the rest was invested at 6%. At the end of year the couple had earned exactly $860 in simple interest. How much did they invest at each rate?

Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Part I 10.00% per annum ------------- Amount invested =x
Part II 6.00% per annum ------------ Amount invested = y
10000
Interest----- 860.00

Part I 10.00% per annum ---x
Part II 6.00% per annum ---y
Total investment
x + 1 y= 10000 -------------1
Interest on both investments
10.00% x + 6.00% y= 860
Multiply by 100
10 x + 6 y= 86000.00 --------2
Multiply (1) by -10
we get
-10 x -10 y= -100000.00
Add this to (2)
0 x -4 y= -14000
divide by -4
y = 3500 - x)
Part I 10.00% $ 6500
Part II 6.00% $ 3500

CHECK
6500 --------- 10.00% ------- 650.00
3500 ------------- 6.00% ------- 210.00
Total -------------------- 860.00

m.ananth@hotmail.ca

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