A 20-gallon container is filled halfway with a mixture that is 90% vinegar and 10% water. How many gallons of water must be added for the mixture to become 60% vinegar and 40% water?
+36915 10 gallons to start with
adding 'x' gallons of water final volume = 10 + x
.9 (10) = amount of vineger
.1(10) = amount of water
amount of vineger before and after water addition is constant
.9(10) = .6(10+x)
9 = 6 + .6x
3 = .6x
x = 5 gallons of water to be added
