A king decided to let a prisoner escape the prison with his
life.
The kind placed 2 marbles in a jar that was glued to a table.
One of the marbles was supposed to be black, and one was supposed
to be blue. If the prisoner could pick the blue marble, he would
escape the prison with his life. If he picked the black marble, he
would be executed.
However, the king was very mean, and he wickedly placed 2 black
marbles in the jar and no blue marbles. The prisoner withnessed the
king only putting 2 black marbles in the jar.
If the jar was not see-through and the jar was glued to the
table and that the prisoner was mute so he could not say anything,
how did he escape with his life? 
pick any marble, throw it outside the window.
then the black marble would remain and then the one picked must
be blue.