The RED and BLACK mystery!

This trick is brilliant. First of all, try it on yourself - you'll be amazed!

Here's what to do:

How does it work?

There are two clues to working it out.

1/ To start with... once you've got the four piles dealt out, it makes no difference how many cards you swap over. Suppose you take one red card across, when you come to take a card back, it will either be red (so it cancels out) or black, which means that the number of red and blacks both decrease by one.

2/ In the example, after the red and black piles are counted out, there must be 14 red cards and 12 black cards left face down, waiting to be dealt out. Suppose by accident you just happened to put all the 12 black cards on pile A and all the 14 red cards on pile B. There would be zero red cards on pile A and zero on pile B - so it's the same number! However, as step 1/ shows, it doesn't matter how you swap them over, you'll still have the same number of reds on pile A as blacks on pile B.

  • Shuffle a normal pack of 52 playing cards.
    Split them into two equal piles of 26 cards face down.

  • Pick up one pile and look at them. Separate the 26 cards into two face-up piles: REDS and BLACKS.

  • Count the cards in the RED pile.

    Pick up the 26 face down cards, and deal the same number of cards face down next to the RED pile.

    FOR EXAMPLE: if there were 12 cards in the red pile, you put 12 cards face down next to it.

    We'll call this face down pile: "A"

    Put the rest of the cards face down next to the BLACK pile. We'll call this face down pile: "B"

    You now have four piles of cards.
    12 red cards
    14 black cards
    Pile A
    12 face down cards
    Pile B
    14 face down cards

  • Pick a number from 1-10

    Let's assume you pick SEVEN.

    Take any seven face-down cards from pile A and mix them in with pile B.

    Then... take any seven face-down cards from pile B and put them on pile A.

    At this point you would have got back to having 12 cards on pile A and 14 cards on pile B.

  • Turn over pile A and count how many cards are RED.

    Turn over pile B and count how many cards are BLACK.

It will be the same number!

Once you've tried it yourself a few times and got used to the routine, try it on your friends!

Pass them a pack of cards, and just tell them what to do. The amazing thing is that... you don't need to touch the cards at any point!
They will be astonished... guaranteed!

If you like this then try Lil's Dead Giveaway Trick!

This trick and many others appear in Brainbenders


Teacher Resources

The Murderous Maths Home Page

Copyright (c) Kjartan Poskitt 2011