Anna-Maria has added 4 quarts of an alcohol in water solution to 1 quart of water and her ending product is a 36% alcohol in water solution. What was the concentration of the 4 quarts of alcohol solution that was added?

The concentration of solution would be the amount of the molecule divided by the volume. In this case, the solution concentration is 36% and the volume is 4 quarts + 1 quarts = 5 quarts. You are asked the concentration before 1 quarts added. The alcohol content should be same for both solutions. The answer should be:

concentration = alcohol content / volume

alcohol content = concentration * volume

alcohol content1 = alcohol content2

36% * 5 quarts = concentration2 * 4quarts

concentration2 = 36% * 5 quarts / 4 quarts = 45%