Measuring 4 litres with a 3-litre and 5 litre jug

Question:

You are given a 3-litre jug and a 5-litre jug.  None of them have measurement lines.

How do you use them to get 4 litres of water? Assume you have a water source available.

Answer:

  1. Fill up the 5-litre jug completely.
  2. Empty the 5-litre jug into the 3-litre jug,

This will leave 2 litres of water in the 5-litre jug while the 3-litre jug will be full.

  1. Completely empty the 3-litre jug.
  2. Empty completely the 5-litre jug into the 3-litre  jug.

This will leave 2 litres in the 3-litre jug while the 5-litre jug will be empty.

  1. Fill up the 5-litre jug completely.
  2. Now pour the water of the 5-litre jug into the 3-litre jug until is full.

Since the 3-litre jug already had 2litre,1 more litre will be used from the 5-litre jug thus leaving 4 litres in the 5-litre jug.