SOLUTION: how many gallons of a 12% solution must be mixed with 6 gallons of a 20% salt solution to obtain a 15% salt solution?

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Question 147757: how many gallons of a 12% solution must be mixed with 6 gallons of a 20% salt solution to obtain a 15% salt solution?
Answer by stanbon(75887) About Me  (Show Source):
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how many gallons of a 12% solution must be mixed with 6 gallons of a 20% salt solution to obtain a 15% salt solution?
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EQUATION:
salt + salt = salt
0.12x + 0.20*6 = 0.15(x+6)
Multiply thru by 100 to get rid of the decimals
12x + 120 = 15x + 90
3x = 30
x = 10 gallons (amount of 12% solution needed for the mixture)
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