SOLUTION: Mariel invested $1oo,ooo in two business accounts earning 8% and 7 1/2% interest. If both investments earn a total of $7,700, how much was invested at each rate ?

Question 889589: Mariel invested $1oo,ooo in two business accounts earning 8% and 7 1/2% interest. If both investments earn a total of $7,700, how much was invested at each rate ?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Part I 8.00% per annum ------------- Amount invested =x
Part II 7.50% per annum ------------ Amount invested = y
100000
Interest----- 7700.00

Part I 8.00% per annum ---x
Part II 7.50% per annum ---y
Total investment
x + 1 y= 100000 -------------1
Interest on both investments
8.00% x + 7.50% y= 7700
Multiply by 100
8 x + 7.5 y= 770000.00 --------2
Multiply (1) by -8
we get
-8 x -8 y= -800000.00
Add this to (2)
0 x -0.5 y= -30000
divide by -0.5
y = 60000
Part I 8.00% $ 40000
Part II 7.50% $ 60000

CHECK
40000 --------- 8.00% ------- 3200.00
60000 ------------- 7.50% ------- 4500.00
Total -------------------- 7700.00

m.ananth@hotmail.ca

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