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The controller​ (money manager) for a small company puts some money in a bank account paying 5​% per year. He uses some additional​ money, amounting to 1/3
the amount placed in the​ bank, to buy bonds paying 66​% per year. With the balance of the​ funds, he buys a 8​% certificate of deposit. The first year the investments bring a return of ​$668. If the total of the investments is​ $10,000 how much is invested at each​ rate?

Respuesta :

$x @ 4%, $x/3 @ 5% , $(10,000- 4x/3) @ 9% 

.04x +.05x/3 + .09(10000 - 4x/3) = 729 

4x + 5x/3 + 9(10000 - 4x/3) = 72900 

19x/3 = 17100, x = 2700 
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$2700 @ 4% 
$900 @ 5% 
$6400 @9%