An innkeeper shows his guests a cask containing some fine ale. He also shows them two empty pitchers, one that could hold 5 pints and another that could hold 3 pints. Neither the cask nor the pitchers have any measurements marked on them. The innkeeper asks, "How is it possible for me to put exactly one pint of ale into each of the pitchers? Of course, I can't use any other equipment, and no marking of measures is allowed."

The innkeeper is allowed to pour ale from the pitchers back into the cask. The innkeeper doesn't know exactly how much ale is in the cask at the start, but it contains more than eight pints.