MathDB
determine maximum real k

Source: Tuymaada 2007, Problem 4

July 15, 2007
combinatorics proposedcombinatorics

Problem Statement

Determine maximum real k k such that there exist a set X X and its subsets Y1 Y_{1}, Y2 Y_{2}, ... ..., Y31 Y_{31} satisfying the following conditions: (1) for every two elements of X X there is an index i i such that Yi Y_{i} contains neither of these elements; (2) if any non-negative numbers αi \alpha_{i} are assigned to the subsets Yi Y_{i} and α1++α31=1 \alpha_{1}+\dots+\alpha_{31}=1 then there is an element xX x\in X such that the sum of αi \alpha_{i} corresponding to all the subsets Yi Y_{i} that contain x x is at least k k.