Back Exploratorium
Mind Reader (Tips for Leaders)

When we showed this card trick to a group of middle schoolers, they gasped in amazement—and all wanted to learn how to do it.

Preparation and Materials
For each pair of players, you will need:
A deck of cards
Photocopies of Mind Reader Instructions and Analyzing Mind Reader (optional)

Planning ChartUsing Mind Reader
With A group

These instructions will help you lead your group through learning the Mind Reader card trick. Don't worry if you are a klutz with cards. This trick requires no manual dexterity (though having a little mental dexterity helps).

Demonstrating the Trick

Read over the Mind Reader instructions and try the trick a few times. Once you are confident that you can do the trick, demonstrate it to your group.

First, ask everyone to get out a pencil and paper so that they can write down the answers to the mathematical questions you’ll be asking. Turn your back while the group selects a card and lays it on a table or desk. Then chose a card yourself, memorize it, and put it down just to the right of the card the group has chosen.

Then follow the steps on Mind Reader instructions. Have the group follow your directions. When they have reached the end of the calculations, turn over the cards and reveal the number that they have calculated.

 Your group will be amazed at your magical abilities.

Give Everyone a Chance to Try It

Have the group divide into pairs and hand out decks of cards and copies of Mindreader instructions. Have each pair do the trick.

You may need to point out to people that the magician doesn’t actually know the number that’s in the other person’s head until the cards are turned over. The magician only knows the card he or she chose. Turning over the cards reveals the number that is the inevitable result of the person’s mathematical calculations. If the person came up with a different number, then the magician and the person should check the math together. If the math is done correctly, the number will match the cards.

Figuring Out How the Trick Works

Every two-digit number has two places: the 10’s place and the 1’s place. In the number 25, for example, there’s a 2 in the 10’s place, which means there are two 10’s, and there’s a 5 in the 1’s place, which means there are five 1’s.

In this trick, the magician gets the person being tricked to do a series of mathematical operations that move the number of the person’s card from the 1’s place to the 10’s place—and puts the number of the magician’s card in the 1’s place.

 Analysing Mind Reader explains exactly how this happens. Younger middle schoolers may not be able to follow the entire explanation, but they may be able to see that the card the victim chooses always moves over to the 10’s place. Even if they don’t understand the complete explanation, middle schoolers of all ages enjoy doing this trick.


Quick Links:

Mind Reader
Analysing Mind Reader
Mind Reader: Tips for Leaders
Using Mind Reader with a Group

Math Explorer Home


© Exploratorium