Puzzle - 38

There was a barrel without any sealing on top left outside a factory gate. It was filled with some water in it. Three friends were passing by that street. One of them guessed that the water is filled more than Half barrel and other said It is less than half barrel. The third one said that the water is filled exactly half Barrel.

If you were asked to determine who is correct without using any measuring equipment, How will you justify who is correct and why?

Answer:
Tilt the barrel until the water barely touches the lip of the barrel, If the bottom of the barrel is visible then it is less than half full. If the barrel bottom is still completly coverd by the water, then it is more than half full.