Math Card Trick

Harry Blackstone Jr

Mathematical Card Trick

In the 1970’s, my father had dinner in Las Vegas with Harry Blackstone, Jr. (1934-1997) He was a famous magician in his time. My father asked Mr. Blackstone to share the secret of his famous card trick, and Harry accommodated him. It has been said that it took a NASA super computer several days to calculate the solution.

Over dinner, my father was taught this amazing mathematical card trick. When he returned from his business trip, my father shared the secret with me. And now, I am sharing it with you!

If you can add 3 to a number 1 through 12, then you can do this card trick.

First divide the deck into 4 stacks. Each stack will have 13 cards (The Jokers are not used)

Divide the stacks into clubs, hearts, spades and diamonds.

Place the stacks on the table in that order.

In the clubs stack, sort as follows: 3, 2, A, K, Q, J, 10, 9, 8, 7, 6, 5, 4 (3 is on top, 4 is on bottom)

In the hearts stack, sort as follows: 6, 5, 4, 3, 2, A, K, Q, J, 10, 9, 8, 7 (6 is on top, 7 is on bottom)

In the spades stack, sort as follows: 9, 8, 7, 6, 5, 4, 3, 2, A, K, Q, J, 10 (9 is on top, 10 is on bottom)

In the diamonds stack, sort as follows: Q, J, 10, 9, 8, 7, 6, 5, 4, 3, 2, A, K (Queen is on top, K is on bottom)

Once the sorted stacks are arranged, begin picking up one card at a time starting with the 3 of clubs, then the 6 of hearts, then 9 of spades, then Queen of diamonds and then continue in that fashion until all of the cards are picked up. At that point, you have a mathematically stacked deck.

The most important step from here is to realize that you must always square cut the deck in order for the mathematical sequence to remain intact. Never cut and fan shuffle the deck once it is set. Always square cut.

The presentation of the trick works like this. Holding the deck in your hands, lightly fan out before your audience. Ask a volunteer to select and pull out a single card from the presented deck. Tell them to keep the card face down. At the point where the card was removed, take the portion of the deck beneath the removed card and place it on top of the section of cards that were above the card that was removed. Do this quickly without drawing attention to it. Do not cut the deck further. Tell the volunteer to show the card to the audience. While he is doing this, simply look at the bottom card and add 3 to it. This will tell you what card he is holding. To determine the suit of his card, simply advance one suit over from your original stacking order of clubs, hearts, spades and diamonds. If the bottom card in a 3 of clubs, then the volunteer’s card is a 6 of hearts, and so on. Use the following values:

A = 1

2 = 2

3 = 3

4 = 4

5 = 5

6 = 6

7 = 7

8 = 8

9 = 9

10 = 10

J = 11

Q = 12

K = 13

Further examples of the computations: if the bottom card is an 8 of clubs, then the volunteer’s card is a Jack of hearts.

Memorize this quick reference table (Number to left is the bottom card. Number to right is volunteer’s card):

A = 4

2 = 5

3 = 6

4 = 7

5 = 8

6 = 9

7 = 10

8 = J

9 = Q

10 = K

J = A

Q = 2

K = 3

When the volunteer returns the card to you, place it either on the top or bottom of the deck. After this, you can continue to square cut the deck and proceed to amaze another volunteer. I hope you enjoyed me sharing this card trick with you. Now practice and perfect your skills.


– Mac Carpeli, Outreach Director