English

Stable Fixed Points of Card Trick Functions

History and Overview 2013-08-16 v1

Abstract

The 21-card trick is a way of dealing cards in order to predict the card selected by a volunteer. We give a mathematical explanation of why the well-known 21-card trick works using a simple linear discrete function. The function has a stable fixed point which corresponds to the position where the selected card reaches at the end of the trick. We then generalize the 21(7 x 3)-card trick to a p x q - card trick where p and q are odd integers greater than or equal to three, determine the fixed point and prove that it is also stable.

Keywords

Cite

@article{arxiv.1308.3396,
  title  = {Stable Fixed Points of Card Trick Functions},
  author = {Jyoti Champanerkar and Mahendra Jani},
  journal= {arXiv preprint arXiv:1308.3396},
  year   = {2013}
}
R2 v1 2026-06-22T01:09:51.832Z