MathDB
polygon combinatorics

Source: 2024 Nigerian MO Senior Round 3 P4

April 28, 2024
combinatorics

Problem Statement

In an island shaped like a regular polygon of nn sides, there are airports at each vertex of the island. The island would like to add kk new airports into the interior of the island, but it must follow the following rules:\\
11. It must be in the interior of the island (none on borders).\\
22. No two airports can be at the exact same location.\\
33. Every triple of 11 new and 22 old airports must form an isoceles triangle.\\
44. No three airports can be collinear.\\
Find the maximum value of kk for each nn
[hide=Harder Version]Replace 11 new and 22 old with 11 old and 22 new.