You have a 3-litre jug, a 5-litre jug, and an unlimited supply of water. How do you get exactly 4 litres of water without estimating?
A windowless room has 3 light bulbs. You’re outside the room with 3 switches, each controlling one of the light bulbs. If you can only enter the room one time, how can you determine which switch controls which light bulb?
There are three boxes of eggs. In each box there is either a set of big eggs, small eggs or big and small eggs mixed. The boxes are labelled (shock) LARGE, SMALL and MIXED but each box is labelled incorrectly. What is the least number of boxes you can open to know which eggs are in which box and why?