2 in x 2.5 in x 0.125 in / 5.1 cm x 6.4 cm x 0.3 cm
Amazing magic possible with these cards that use interesting math principles. There are 9 hardwood cards from 3 different woods, each with a different number from 1 to 9 on one side and they are blank on the other side. The cards are precision laser cut from 1/8" woods. The shape of each card is a head and each is identical at about 2.3" x 2"
Here is how the trick may go: (note, see video for details) Ask someone to pick 1 card of each color and make a pile. Then ask them (or a different person) do pick from the remaining cards and do the same, ie, select one card from each color. You will now have 3 sets of cards each with 1 of each color. Ask them to arrange the sets in any color order that they want, but in the same color order for each pile. (such as light wood, dark wood, red wood). Have them look at each set of 3 cards. There are essentially three 3-digit numbers. Have them add these 3 numbers together. Surprisingly, no matter how that cards are arranged, you will always be able to determine the number. I won't spoil the secret here, but watch the video if you want to know how its done. It can be used as a straightforward prediction or even more fun as a magic book test. For example, after they have added the numbers, ask them to take the first 3 digits of their sum and turn to that page number Then ask them to read across to the word represented by the 4th digit (it will be the 5th word). Then have them write down the word. You will be able to predict that word! You can even do it with a handful of books and let them choose the book, as long as you have prepared ahead of time.
You may find other fun ways to use this amazing math fact puzzle, such as, can you arrange the cards in a 3x3 grid such that each row, column, and diagonal adds to 15? Special thanks to Alan JAckson of the UK for his suggestion on this puzzle.