You want to boil a two-minute egg. If you only have a three-minute timer (hourglass), a four-minute timer and a five-minute timer, how can you boil the egg for only two minutes?
A father is locked up in jail. His wife has gone bankrupt. Their male child has to sell his hotel in order to gain some money. Yet their girl child does not care and is quite happy.
You order chicken wings at KFC in the boxes of 6, 9 and 20. What is the largest number of wings that you cannot obtain by buying in any combination of the boxes?