Problem

Source: Bundeswettbewerb Mathematik 2022 Round 1 P2

Tags: combinatorics, combinatorial geometry, Triangle, Germany



Eva draws an equilateral triangle and its altitudes. In a first step she draws the center triangle of the equilateral triangle, in a second step the center triangle of this center triangle and so on. After each step Eva counts all triangles whose sides lie completely on drawn lines. What is the minimum number of center triangles she must have drawn so that the figure contains more than 2022 such triangles?