SOLUTION: A mixture of alchohol and water contains 15% alchohol. How many gallons of alchohol must be added to 5 gallons. of this mixture to make it a 20% mixture.

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Question 1082442: A mixture of alchohol and water contains 15% alchohol. How many gallons of alchohol must be added to 5 gallons. of this mixture to make it a 20% mixture.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
In the 5 gallon mixture,
5%2A%2815%2F100%29=75%2F100=3%2F4
3/4 gallon is alcohol.
So to get it to 20%, add X.
%283%2F4%2BX%29%2F%285%2BX%29=20%2F100
100%283%2F4%2BX%29=20%285%2BX%29
75%2B100X=100%2B20X
80X=25
X=25%2F80
X=5%2F16gallons