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Question 365023: A man who recently won a lottery wishes to invest $100,000. Part of this amount is invested at 12% and part of it at 15%. If the total interest earning should be $14 115 per year, how much should be invested at 15% and how much at 12%.
I tried many solutions but this is the only one that i think is somewhat right.
14115 = .12x + .15x
Answer by nerdybill(7384)   (Show Source):
You can put this solution on YOUR website! A man who recently won a lottery wishes to invest $100,000. Part of this amount is invested at 12% and part of it at 15%. If the total interest earning should be $14 115 per year, how much should be invested at 15% and how much at 12%.
I tried many solutions but this is the only one that i think is somewhat right.
14115 = .12x + .15x
.
Well, you're close...but, you can't use the same variable to represent both amounts.
.
Let x = amount invested at 12%
then because his total investment was $100,000 we have
100000-x = amount invested at 15%
.
14115 = .12x + .15(100000-x)
14115 = .12x + 15000 - .15x
14115 = 15000 - .03x
-885 = -.03x
$29,500 = x (amount invested at 12%)
.
Amount invested at 15%:
100000-x = 100000-29500 = $70,500
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