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riddles >> hard >> 5 Card Magic Trick
(Message started by: GnomeSain on May 21st, 2011, 6:07pm)

Title: 5 Card Magic Trick
Post by GnomeSain on May 21st, 2011, 6:07pm
By the pigeon-hole principle, you're going to have least a pair of the same suit. Call these cards A and B. For simplicity suppose the ranks are just from 1 to 13. We define the distance d(A,B) to be how many steps it to go from A forward mod 13 to B. So for example, d(3,5) = 2 and d(9,3) = 7. Then, for any A and B , we are guarenteed either d(A,B) is less than or equal to 6 or d(B,A) is less than or equal to 6.

If d(A,B) is less than or equal to 6, we will guess B and flip A on the fourth. If d(B,A) is less than or equal to 6, we will guess A and flip B on the fourth.

That means, the first three cards X,Y and Z will have to convey what d(A,B) or d(B,A) is. We use the usual card ordering on them and note the total arrangement of orderings is 3! = 6. So we have just enough to convey the distance from A to B.


Title: Re: 5 Card Magic Trick
Post by arun gupta on Apr 3rd, 2012, 10:13pm
I thought this is one of the best and easy trick. I tried and do it many times in a day.
Thanks!

Title: Keith Gilabert. 5 Card Magic Trick
Post by keithgilabert on May 13th, 2012, 8:23pm
That is a really cool trick!

Thanks,

Keith Gilabert

Title: Re: 5 Card Magic Trick
Post by RandyMagic on Nov 13th, 2014, 2:37am
Easy and cool trick! I tried myself and did not know it would be so much fun!



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