You Math Guys

[Sixpence]

I learned a card trick and cannot figure out the math to it. Take a deck of cards, count out 26 cards one on top of the other in a pile face up(make note of the 7th card), then flip the pile over face down.

Now, with the remaining cards, flip the top one over. If it is a 6, count out 4 more cards from the remaining deck(make a solitaire like column) to equal ten. Now start another column by flipping over another card from the remaining deck, if it is a King, do not flip over another card(10 through king = 10). Now start a third column by flipping over another card from the remaining deck, if it is a 2, count out 8 cards from the remaining deck to equal 10. Only make three columns.

Now put the remaining cards face down on the cards you counted out originally. Now add up the three cards that started the three columns  6+K(10)+2= 18. Now count out 18 cards from the face down deck by flipping them over one by one. The 18th card will be the 7th card you noted as you counted out the original 26. What ever those three cards add up to @ the top of the three columns, it will always be the 7th card.

[ra]

I like cards.

[vorticon]

Originally posted by ra
I like cards.

i prefer ice cream.

[JB73]

unless there's sleight of hand / card control it's not a "trick"

it's a mathematical example that many children learn as their first "trick".

kind of like when magicians tell you you will pick something out of a group, the whole time forcing you to the spot they want.

those never really impressed me.





back on the topic, that equation is based on the 1/2 of the deck (26 ... NO 26x2 does NOT equal 42 LOL)

the number of cards you are taking out of the pack (counting to ten) are the real part of the formula.

[Sixpence]

Originally posted by JB73
those never really impressed me.

You have to be pretty good at math to come up with that, I mean, each card is random at the top of each column. How does adding those three cards come to the 7th card?

[majic]

Originally posted by Sixpence
I learned a card trick and cannot figure out the math to it. Take a deck of cards, count out 26 cards one on top of the other in a pile face up(make note of the 7th card), then flip the pile over face down.

Now, with the remaining cards, flip the top one over. If it is a 6, count out 4 more cards from the remaining deck(make a solitaire like column) to equal ten. Now start another column by flipping over another card from the remaining deck, if it is a King, do not flip over another card(10 through king = 10). Now start a third column by flipping over another card from the remaining deck, if it is a 2, count out 8 cards from the remaining deck to equal 10. Only make three columns.

Now put the remaining cards face down on the cards you counted out originally. Now add up the three cards that started the three columns  6+K(10)+2= 18. Now count out 18 cards from the face down deck by flipping them over one by one. The 18th card will be the 7th card you noted as you counted out the original 26. What ever those three cards add up to @ the top of the three columns, it will always be the 7th card.

You messed me up for a while there until I figured out you meant the 7th card from the top of the first pile not the bottom.

Here's the math:

a=1st card value
b=2nd card value
c=3rd card value

52-[(10-a+1)+(10-b+1)+(10-c+1)+(a+b+c)]=19

(I'll get to why it always equals 19 in a sec.)

The 52 is your totla starting cards.

The (10-a+1) represents how many cards you take out of each of the 3 draws.  (The +1 part represents the actual card drawn.)

The (a+b+c) is from your post, the values of the cards added together.

Everthing in the brackets [] represents the number of cards you tke away.  Since you find each variable as a positive and a negative they cancel each other out.  So:

52-[(10+1)+(10+1)+(10+1)]=19
52-[11+11+11]=19
52-33=19

The seventh card from the top (of 26) has those 19 cards beneath it.

The key of course is eliminating the variables.

[JB73]

Originally posted by Sixpence
You have to be pretty good at math to come up with that, I mean, each card is random at the top of each column. How does adding those three cards come to the 7th card?

i have a book on all of those, most were made around the turn of the century, before and after houdini.

lots of mathmeticians were looking into random numbers then, and it was a way to test some of that stuff.



quick question: with a fresh deck in order just opened, how many shuffles does it take to get assured randomness?

[hawker238]

Seven.

[Sixpence]

That's good stuff

[Holden McGroin]

Originally posted by majic
So:

52-[(10+1)+(10+1)+(10+1)]=19
52-[11+11+11]=19
52-33=19

Louis Farrakan had a speech in front of the Lincoln Memorial all about this card trick.  Everything adds up to 19.