SOLUTION: how many gallons of an 80% solution must be mixed with 90 gallons of 15% solution to make a 70% solution?

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Question 779067: how many gallons of an 80% solution must be mixed with 90 gallons of 15% solution to make a 70% solution?
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
how many gallons of an 80% solution must be mixed with 90 gallons of 15% solution to make a 70% solution?
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Equation:
active + actve = active
0.15*90 + 0.80x = 0.70(90+x)
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15*90 + 80x = 70*90 +70x
10x = 55*90
x = 9*55 = 495
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Cheers,
Stan H.
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