SOLUTION: Ivan had $10,000 to invest. He invested some in an account that paid 7% simple interest per year and some in an account that paid 5% simple interest per year. After 1 year he rec

Question 739875: Ivan had $10,000 to invest. He invested some in an account that paid 7% simple interest per year and some in an account that paid 5% simple interest per year. After 1 year he received a total of $680 in interest. How much did he invest in each account?
(I tried to set up a table, but all I know is the amount of time, the total principal and the total interest. I can't figure out what variables to use or where to place them to form an equation to solve.
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
10000
Interest----- 680.00

Part I 5.00% per annum ---x
Part II 7.00% per annum ---y
Total investment
x + 1 y= 10000 -------------1
Interest on both investments
5.00% x + 7.00% y= 680
Multiply by 100
5 x + 7 y= 68000.00 --------2
Multiply (1) by -5
we get
-5 x -5 y= -50000.00
Add this to (2)
0 x 2 y= 18000
divide by 2
y = 9000
Part I 5.00% $ 1000
Part II 7.00% $ 9000

CHECK
1000 --------- 5.00% ------- 50.00
9000 ------------- 7.00% ------- 630.00
Total -------------------- 680.00

m.ananth@hotmail.ca

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