MathDB
IMC 2017 Problem 10

Source:

August 3, 2017
college contestsIMCimc 2017

Problem Statement

Let KK be an equilateral triangle in the plane. Prove that for every p>0p>0 there exists an ε>0\varepsilon>0 with the following property: If nn is a positive integer, and T1,,TnT_1,\ldots,T_n are non-overlapping triangles inside KK such that each of them is homothetic to KK with a negative ratio, and =1narea(T)>area(K)ε, \sum_{\ell=1}^n \textrm{area}(T_\ell) > \textrm{area}(K)-\varepsilon, then =1nperimeter(T)>p. \sum_{\ell=1}^n \textrm{perimeter}(T_\ell) > p.