If we assume that the barrel was filled with something to begin with, filling it with air will make it lighter.
result - a hole
There are two plastic jugs filled with water. How could you put all of this water into a barrel, without using the jugs or any dividers and still tell which water camr from which jug?
I don't have a predecessor You've seen nothing like me before
If not for creativity There wouldn't be a place for me
Thankfully, the world we live in Will never stop discoverin'
Otherwise, I would not exist And monotony would persist
What am I?
A criminal has to carry a sack of stones from one side of the prison to another.
What can he put in the sack that will make it lighter?