MathDB
Deck of cards labelled with subsets

Source: 239 School Open MO, 2023, Junior league, Problem 8

April 1, 2023
combinatoricsset theory

Problem Statement

Let nn{} and kk{} be natural numbers, with n>2kn > 2k. In the deck of cards, each card contains a subset of the set {1,2,,n}\{1, 2, \ldots , n\} consisting of at least k+1k+1, but no more than nkn-k elements. Each mm-element set is written exactly on mkm-k cards. Is it possible to split these cards into n2kn- 2k stacks so that in each stack all subsets on the cards are different, and any two of them intersect?