target of 100 equal equilaterals - All-Russian MO 2001 Regional (R4) 9.4
Source:
September 26, 2024
combinatoricscombinatorial geometryequilaterals
Problem Statement
The target is a triangle divided by three families of parallel lines into equal regular triangles with single sides. A sniper shoots at a target. He aims at triangle and hits either it or one of the sides adjacent to it. He sees the results of his shooting and can choose when stop shooting. What is the greatest number of triangles he can with a guarantee of hitting five times?