Place three glasses on the table, two facing up and one down as shown in Fig. 1. Challenge a volunteer to get all three glasses face down, turning two at a time and using exactly three moves.
It won?t be long before they give up and beg you for the answer. Well here it is: first turn 2 & 3 then 1 & 3 and then 2 & 3. Practise these moves until you can do them really fast. They won?t be able to copy you even after they have seen you do it!