MathDB
rioplatense(2005/6)

Source:

September 3, 2006
integrationcombinatorics unsolvedcombinatorics

Problem Statement

Let kk be a positive integer. Show that for all n>kn>k there exist convex figures F1,,FnF_{1},\ldots, F_{n} and FF such that there doesn't exist a subset of kk elements from F1,...,FnF_{1},..., F_{n} and FF is covered for this elements, but FF is covered for every subset of k+1k+1 elements from F1,F2,.....,FnF_{1}, F_{2},....., F_{n}.