A Mathematical Card Trick

What You Need:

• Deck of playing cards
• Pencil and scratch paper (for computation)

What You Do:

1. Find someone to trick.
2. Ask that person to pick a card from the deck and keep it secret.
3. Have them double the face value of the card (aces = 1, jacks = 11, queens = 12, and kings = 13).
4. Ask them to add 3 to their result.
5. Ask them to multiply this by 5.
6. Have them add 1 if the card is a club, 2 if it is a diamond, 3 if it is a heart, and 4 if it is a spade.
7. Ask them to tell you their number.
8. To predict the card, subtract 15 from the final total. The right digit of the answer represents the suit of the card (1 = club, 2 = diamond, 3 = heart, 4 = spade). The left digit or digits is the number value of the card. For example, if their result is 83, the card is the 8 of hearts. If the result is 134, the card is the king of spades.

Can you figure out how this trick works?