Mathemagic Numbers Cards Generator

By Fitz and Rajiv

The Magic Trick

1. Ask a member of your audience to think of a whole number betweem 1 and the largest number printed on your set of mathemagic cards.
2. Show them each of your cards, one by one. Ask them if the number they thought of is on that card.
3. Once they have answered for each card, you reveal to them what their number is.

How it is Done

• As you show them or hand them each card, one by one, look at the first number on the card.
• If they answer yes to their secret number being on the card, add the first number on that card to a running total.
• When all the cards have been exhausted, your running total will match their secret number.

Tips

• The trick has a better effect if you compute your running total mentally while only giving a casual glance to the first number on each card before or while you show or hand it to your audience particpant.
• Magician version: Hand the deck of cards face down to the audience particpant. Tell them to pick up each card from the top, one by one, look at it without showing you the card, and put it face down in another pile. You know the order of cards before you hand them the deck, and you remember the value of the first number on each card.
• Consider using the deck with 7 cards, and ask them to think of a number between 1 and 100 (instead of 123). 100 feels more natural. The other numbers' presence on the cards even though they are not used might add to the mystery of the trick.
• Magician version: Consider using the deck with 10 cards, and ask them to think of a number between 1 and 1,000 (instead of 1024). 1,000 feels more natural.

Credits

Thanks to Vijit Sharma and family for introducing Rajiv and Fitz to this math magic trick. Rajiv and Fitz coauthored the JavaScript here that generates the cards. Fitz figured out the generalized algorithmic pattern of numbers to be generated that works for each card and for any number of cards.