Answer:
Six glasses are in a row. The first three are filled with milk and the last three are empty. By moving only one glass, can you arrange them so that the full and the empty glasses alternate?
What always comes into a house through the keyhole?
What was the longest river in the world before the Amazon River was discovered?
What is as big as you are and yet does not weigh anything?
How can you add eight 6s together so that the total adds up to 750?
Almost everyone needs it, asks for it, gives it. But almost nobody takes it.