How does the math card trick work?

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Whalstib
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Here's the video:
http://www.flixxy.com/math-magic-card-trick.htm

Just the idea that the odd even of the up down never reveals the cards baffles me..

I got to find a deck of cards!

If you know don't blow it right away! Hints ok...

Warren

OK In the form of an edit...

I can see how the 1st and last card are intentionally inserted into a slot that will always be 2 of the last 3 cards. But the 3rd is random. Isn't it?
 
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OK..

That wasn't too hard with a deck of cards to figure out...It's weird how you think by choosing you have a choice!

Warren
 
Hint: look at the order he places the 3 layers on top of each other. What does this imply about the position of the 3 cards ;)
 
Right!

But you wouldn't think it's ... well ...

The idea "you" cutting the deck implies some uncertainty which there clearly is not!

W
 
Yeah it looks really surprising at first sight. Once you start analysing it in more detail however it doesn't take very long to realize that the point where the cards are cut has absolutely no effect at all on the positions in the deck where the three "trick" cards eventually go. It's not hard to show that they will always be in positions (from the top) of 6, 22 and 38 when he starts the "up down up down etc" deal out.
 
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Yep

Put pencil to paper and becomes apparent.

It still seems like it should not be though...That's the trick part!

W
 
Whalstib said:
Yep

Put pencil to paper and becomes apparent.

It still seems like it should not be though...That's the trick part!

W
That's the great part. Non-intuitive = incomprehensible = MAGIC.