Question 314779: 1. Sam invested some money at 7% and then invested $4,000 more than twice this amount at 9%. His total annual income from the two investments was $2,860. How much was invested at 9%?
2. How many liters of a 10% alcohol soultion must be mixed with 30 liters of a 40% solution to get a 20% solution?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Sam invested some money at 7% and then invested $4,000 more than twice this amount at 9%. His total annual income from the two investments was $2,860. How much was invested at 9%?
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0.07x + 0.09(2x+4000) = 2850
Multiply thru by 100 to get:
7x + 18x + 36000 = 285000
25x = 249000
x = $9960 (amt invested at 7%)
2x+4000 = 2*9960+4000 = $23,920 (amt. invested at 9%
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2. How many liters of a 10% alcohol solution must be mixed with 30 liters of a 40% solution to get a 20% solution?
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alcohol + alcohol = alcohol
0.10x + 0.40*30 = 0.20(x+30)
Multiply thru by 100 to get:
10x + 40*30 = 20x + 20*30
10x = 20*30
x = 60 liters (amt. of 10% solution needed for the mixture)
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Cheers,
Stan H.
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