SOLUTION: carter fenton earned $12,000 last year by giving tennis lessons. He invested part of the money at 3% simple interest and the rest at 4%. In one year, he earned a total of $440 in i

Question 882353: carter fenton earned $12,000 last year by giving tennis lessons. He invested part of the money at 3% simple interest and the rest at 4%. In one year, he earned a total of $440 in interest. How much did hr invest at each rate?
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
12000
Interest----- 440.00

Part I 3.00% per annum ---x
Part II 4.00% per annum ---y
Total investment
x + 1 y= 12000 -------------1
Interest on both investments
3.00% x + 4.00% y= 440
Multiply by 100
3 x + 4 y= 44000.00 --------2
Multiply (1) by -3
we get
-3 x -3 y= -36000.00
Add this to (2)
0 x 1 y= 8000
divide by 1
y = 8000
Part I 3.00% $ 4000
Part II 4.00% $ 8000

CHECK
4000 --------- 3.00% ------- 120.00
8000 ------------- 4.00% ------- 320.00
Total -------------------- 440.00

m.ananth@hotmail.ca

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