A king decided to let a prisoner try to escape the prison with his life. The king 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 picked 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 jars without any blue marbles. The prisoner witnessed the king only putting 2 black marbles in the jars.
The jars were not see-through, the jars were glued to the table and the prisoner was mute so he could not say anything. How did he escape with his life?
The prisoner grabbed one of the marbles from the jar, swallowed it, and picked up the other marble and showed everyone. The marble was black, and since the other marble was swallowed, it was assumed to be the blue one. So the mean king had to set him free.