MathDB
Cutting up an equilateral triangle

Source: All-Russian MO 1999

December 31, 2012
complementary countingcombinatorics unsolvedcombinatorics

Problem Statement

An equilateral triangle of side nn is divided into equilateral triangles of side 11. Find the greatest possible number of unit segments with endpoints at vertices of the small triangles that can be chosen so that no three of them are sides of a single triangle.