Two workers in a brewery are trying to settle an argument over how much beer is inside a barrel. One worker thinks the barrel is more than half full while the other says it’s less than half full.
How can they settle the argument without using any measuring tools?
Note: the top of the barrel can be easily removed.
They must tilt the barrel until the water reaches the rim of the barrel. If they can see the bottom of the barrel then it is less than half full.