SOLUTION: how much water must be added to 300 gallons of 85% alcohol in order to reduce it to 70% alcohol?

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Question 414153: how much water must be added to 300 gallons of 85% alcohol in order to reduce it to 70% alcohol?
Found 2 solutions by josmiceli, Alan3354:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let w = gallons of water to be added
given:
.85%2A300+=+255 are gallons of alcohol in 85% mixture
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255%2F%28w+%2B+300%29+=+.7
255+=+.7%2A%28w+%2B+300%29
255+=+.7w+%2B+210
.7w+=+45
w+=+64.286 gallons
64.286 gallons of water must be added

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
300 gallons of 85% alcohol has 300*0.85 = 255 gallons of alcohol
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For 255 gallons to be 70%, water has to be 30%
Total = 255/0.7 = 2550/7 =~ 364.286
Add 364.219 - 300 = 64.286 gallons of water