On his birthday , a king was supposed to let a prisoner try to escape his prison with his life. The king was to place two 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 two black marbles in the jars and no blue marbles.
Now the prisoner saw the king putting only two black marbles in the jars, and realized the pickle he was in. How did he escape with his life , knowing that there were two black marbles in the jar?
well its obvious he put his hand in the jar pulled out a marble but then does not show it, and instead says lets see what marble is left in the jar, and thus if the king would be forcedl to expose his injustice or set him free... or something like that.
He said to the king "You pick one first and I'll go second". When the king produces a black marble, the prisoner says (without taking a marble from the jar) "The blue one is mine then".