In a container two gallons of a mixture of spirit and water contains 10% of water. They are added to four gallons of another mixture, containing 10% of water and half a gallon of water is then added to the whole. Find the percentage of water in the resulting mixture.

First mixture: 2 gallons with 10% water = 0.2 gallons water. Second mixture: 4 gallons with 10% water = 0.4 gallons water. Total water before addition: 0.2 + 0.4 = 0.6 gallons. After adding 0.5 gallons water: total water = 1.1 gallons. Total mixture = 2 + 4 + 0.5 = 6.5 gallons. Percentage of water = (1.1 / 6.5) * 100 = 16.92%, which rounds to approximately 17%.