What is the secret behind this math card trick?

[Whalstib]

I've spent a few minutes...or more<G> trying to crack this one...

http://www.metacafe.com/watch/535213/math_card_trick_revealed/

...to no avail.

After trying it much becomes apparent but not the final answer.

I tried it 5 times and it worked every time!

Warren

 

[MotoH]

It works on how the cards are laid down. That is about as far as I can explain that without trowing gibberish!

If you like the math card tricks check out CardTrickTeacher (Mismag822) on youtube. he has a whole bunch of math card tricks!

 

[CEL]

It only matters the three first blocks of cards, since all the others are discarded. Suppose the cards that initiate each block are A, B and C respectively.
You have 11 - A cards in the first block, 11 - B in the second and 11 - C in the third, or 33 - (A + B + C) in the total.
Since there are 52 cards in the deck, the remaining cards are 52 - [33 - (a + B + C)] or 19 + A + B + C.
You discard 19 cards from the remaining. You have A + B + C cards.
You uncover the top cards of the first and third blocks (A and C).
You separate A + C cards from the remaining and you get B, the top card of the center block.

 

[beaster]

The thing is, it really doesn't involve math at all when you think about it, which makes it simpler... It's memory.

Notice he doesn't shuffle the stacks, so it may involve some math shenanigans, but its also a memory trick possibility.

I just tried it both ways, and both ways work (math and memory)

 

[TheStatutoryApe]

I just tried it both ways, and both ways work (math and memory)

The best part of the trick though is using the formula and telling the person you are showing the trick exactly what you are doing the whole way through. The average person will be just as baffled, if not more so. Every person I have shown it to has believed I was pulling a fast one on them even though I told them at the beginning it was purely a trick of math.

 

[boboYO]

Yea the point of the trick is not that you know what the top card is, but that the number of cards you are holding is the same as the top card.