Problem

You have a 5 litre and a 3 litre jug, you need exactly 4 litres. How will you get it? You have as much water as you need.

Answer 1

Fill the 5 litres, use that to fill the 3 litre jug, leaving 2 litres in the large jug. Tip out the 3 litre jug. Now pour the remaining 2 litres into the 3 litres jug. Refill the 5 litre and use it to top up the 3 litre jug, using one litre. You are left with 4 litres in the large jug.

Answer 2

Fill the 5 litre jug, then use that to fill the 3 litre jug, leaving 2 litres in the large jug. Tip out the 3 litre jug and put the remaining 2 litres inanother container (or your pocket). Now repeat leaving the 2 litres in the large jug and return the first 2 litres to the large jug, giving you 4 litres.

Picture from: http://www.crystalpurewateraz.com/images/PouringWater.jpg