You are blind and sitting at a table with 100 coins on it. You know exactly 50 coins are showing heads and the rest tails, and you can tell by feel where the coins are, but you are unable to see or feel whether a particular coin is showing heads or tails.
Your task is to divide the coins on the table into two sets each of which has the same number of heads and the same number of tails as the other. How can you do it?