A former boss of mine used to love astounding our students with this seemingly simple math magic trick. First, he'd have you pick a number from 1 to 63. He would show you each card, asking you if your number appeared on that card. After showing you all six cards, he was always able to pinpoint your number within seconds.
I like to think I'm pretty good at math puzzles and tricks, but I couldn't figure this one out until he explained it to me. Can you figure out the trick?