SOLUTION: A SIX LITER MIXTURE OF ALCOHOL AND WATER IS 75% ALCOHOL.HOW MUCH ALCOHOL MUST BE ADDED TO THE EXISTING MIXTURE TO PRODUCE A MIXTURE THAT IS 80% ALCOHOL?

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Question 164341: A SIX LITER MIXTURE OF ALCOHOL AND WATER IS 75% ALCOHOL.HOW MUCH ALCOHOL MUST BE ADDED TO THE EXISTING MIXTURE TO PRODUCE A MIXTURE THAT IS 80% ALCOHOL?
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
6*.75+x=.80(6+x)
4.5+x=4.8+.8x
x-.8x=4.8-4.5
.2x=.3
x=.3/.2
x=1.5 liters of pure alcohol is needed.
Proof:
6*.75+1.5=.8(6+1.50
4.5+1.5=.8*7.5
6=6