You have jugs with no markings — just their full sizes, like 3 litres and 5 litres — and you need exactly 4 litres. You can fill a jug from the tap, empty it out, or pour one jug into another until the first is empty or the second is full.
The secret is that pouring a full jug into a part-full one leaves a measured remainder behind. Fill the 5, pour into the 3, and 2 litres stay in the 5. Keep going and every amount you need appears.
Harder levels use bigger jugs and three-jug problems; Share it out is the old puzzle of splitting a full jug into two equal halves with only pouring.
Measure an exact amount of water using jugs with no markings — fill, empty and pour.
The full guide, with a worked example and common mistakes: How to play Water Jugs.
Every puzzle here can be solved; the counter shows the fewest moves needed.
Yes — fill, empty and each pour are one move each.
There is no tap: one jug starts full and you must split it into two equal halves by pouring between the jugs.