Binary Magic trick cards. In this simple trick you can guess your volunteer's number by simply looking at your 3d printed cards. The trick works by having a volunteer pick a number on the cards and then hand you all the cards with that number on it. Then with a little bit of magic, you will be able to guess their number. 

Attached is instructions on how to do the trick. It is super easy and involves no slight of hand or skill. You just need to be able to do basic arithmetic in your head. This trick has been around forever, but I made this version as a remix cse4k12.org under Creative Commons Attribution-Share Alike 3.0 Unported License.