You have a 12 litre jug, an 8 litre jug, and a 5 litre jug. None of the jugs have any markings on them. The 12 litre jug is full, and the other two are empty.
How can you divide the 12 litres of water in such a way that two of the jugs (the 12 litre and the 8 litre jugs) have exactly 6 litres of water in them, and the third (the 5 litre jug) is empty?
Jugs: 12 0 0
fill the 8 litre jug from the 12 litre one, then fill the 5 litre jug from the 8 litre one.
Jugs: 4 3 5
Empty the 5 litre jug into the 12 litre one, and the 8 litre one into the 5 litre one.
Jugs: 9 0 3
Fill the 8 litre jug from the 12 litre one, then the 5 litre one from the 8 litre one.
Jugs: 1 6 5
Finally empty the 5 litre one into the 12 litre one.
Jugs: 6 6 0