Three coins are placed in your hand. When you open your hand again the number of coins has increased to five.
Before your performance secretly stick two coins to the underside of your table with plasticine. Place three coins on the table. Let everyone see that your hands are empty. With your right hand, scoop the coins from the table into your left hand. At the same time, the left fingers reach under the table and take the two hidden coins. Open your left hand and the coins have magically multiplied.