How do you beat Water Jars on the Coolmath website

Add 5 liters to the 7 liter bottle. Add 5 more to the 7 liter bottle; now you have 3 liters. Dump out the water from the 7 liter bottle. Then add the 3 liters to the 7 liter bottle. Fill the 5 liter bottle again and dump it into the 7 liter bottle. Dump out the water in the 7l bottle and add 1 liter to the 7 liter bottle. Add 5 liters to the 7 liter bottle and there you have it.