The Kruskal Count is a card trick invented by Martin Kruskal in which a magician “guesses” a card selected by a subject according to a certain counting procedure. With high probability the magician can correctly “guess” the card. The success of the trick is based on a mathematical principle related to coupling models for Markov chains. This paper analyzes in detail two simplified variants of th...

We present an analog of the well-known Kruskal-Katona theorem for the poset of subspaces of PG (n; 2) ordered by inclusion. For given k; ` (k < `) and m the problem is to nd a family of size m in the set of`-subspaces of PG (n; 2), containing the minimal number of k-subspaces. We introduce two lexicographic type orders O 1 and O 2 on the set of`-subspaces, and prove that the rst m of them, take...

Approximations to the Kruskal-Katona theorem are stated and proven. These approximations are weaker than the theorem, but much easier to work with numerically.