Red vs black - Revision history

Oscarlevin: Reverted edits by Ocafaromy (talk) to last revision by Oscarlevin

2010-11-24T12:51:17Z

Reverted edits by Ocafaromy (talk) to last revision by Oscarlevin

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	==Puzzle==		==Puzzle==

Ocafaromy at 23:55, 23 November 2010

2010-11-23T23:55:23Z

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	==Puzzle==		==Puzzle==

Oscarlevin at 16:25, 18 May 2010

2010-05-18T16:25:21Z

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			==Puzzle==

	You have a regular deck of 52 playing cards which you shuffle very well. You are instructed to peel off two cards at a time and place them in one of three piles:		You have a regular deck of 52 playing cards which you shuffle very well. You are instructed to peel off two cards at a time and place them in one of three piles:
	* Put both cards in the right pile if both cards are red.		* Put both cards in the right pile if both cards are red.

Oscarlevin: Created page with 'You have a regular deck of 52 playing cards which you shuffle very well. You are instructed to peel off two cards at a time and place them in one of three piles: * Put both car…'

2010-04-22T15:49:56Z

Created page with 'You have a regular deck of 52 playing cards which you shuffle very well. You are instructed to peel off two cards at a time and place them in one of three piles: * Put both car…'

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You have a regular deck of 52 playing cards which you shuffle very well. You are instructed to peel off two cards at a time and place them in one of three piles:
* Put both cards in the right pile if both cards are red.
* Put both cards in the left pile if both cards are black.
* Put both card in the middle pile if one is red and one is black.

You do this until you have run through all 52 cards. What is the probability that the number of cards in the right pile will be equal to the number of cards in the left pile?

==Variation==

What if you start with a deck that has 4 more black cards than red cards. How will the piles end up?

==Note==

This makes (in fact, originally was) a great magic trick: make a prediction, then run through the cards.

[[Category: Probability]]
[[Category: Number theory]]