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Problem of the Month – March 2026

On each vertex of a regular n ≥ 3 sided polygon there is a real number so that the sum of these n numbers is zero. For any two vertices of the polygon with numbers x and y consider the line passing through these vertices dividing the polygon into two parts. Let the sum of numbers written on one of these parts be A and the sum of numbers written on the other part be B. If

|x − y| ≥ |A − B|

we say that this pair of vertices is good. For each fixed n find the minimal possible number of good vertex pairs.

 

Correct Solutions by,

  • Toshihiro Shimizu Kawasaki, Japan
  • Abdulkadir Tanrıverdi Eskişehir
  • Ahmet Yüksel Aydın
  • Murat Burç Soma, Manisa
  • Magnus Jakobsson Lund, Sweden
  • Roger Bengtsson Lund, Sweden
  • Tamer Türkoğlu Bilkent University alumnus
  • Mustafa Kaynak Gaziantep

Solution: https://math.bilkent.edu.tr/Problem/2603a.pdf