SOLUTION: Sergio invests part of his 90,000 PESOS at 4% and the rest at 3%. How much money is invested at each rate if he makes a total income of 3,100 PESOS annually?

Question 724061: Sergio invests part of his 90,000 PESOS at 4% and the rest at 3%. How much money is invested at each rate if he makes a total income of 3,100 PESOS annually?
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
Part I 3.00% per annum ------------- Amount invested =x
Part II 4.00% per annum ------------ Amount invested = y
90000
Interest----- 3100

Part I 3.00% per annum ---x *
Part II 4.00% per annum ---y
Total investment
x + 1 y= 90000 -------------1
Interest on both investments
3.00% x + 4.00% y= 3100
Multiply by 100
3 x + 4 y= 310000.00 --------2
Multiply (1) by -3
we get
-3 x -3 y= -270000.00
Add this to (2)
0 x 1 y= 40000
divide by 1
y = 40000
Part I 3.00% pesos 50000
Part II 4.00% pesos 40000

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