at most 400 unit discs are inside a square of side 100
Source: 1995 German Federal - Bundeswettbewerb Mathematik - BWM - Round 1 p4
January 27, 2020
combinatoricscirclessquarecombinatorial geometry
Problem Statement
A number of unit discs are given inside a square of side such that
(i) no two of the discs have a common interior point, and
(ii) every segment of length , lying entirely within the square, meets at least one disc.
Prove that there are at least discs in the square.