Arrange twelve pennies in a circle, as shown in the illustration. 
Now take up one penny at a time and, passing it over two pennies, place it on the third penny. 
Then take up another single penny and do the same thing, and so on, until, in six such moves, you have the coins in six pairs in the positions 1, 2, 3, 4, 5, 6. 
You can move in either direction round the circle at every play, and it does not matter whether the two jumped over are separate or a pair. 
This is quite easy if you use just a little thought.