tank of enemy at one of the 13 x 13 fields
Source: 2020 Dürer Math Competition Finals E1.2
November 29, 2020
combinatorics
Problem Statement
We are given a map divided into fields. It is also known that at one of the fields a tank of the enemy is stationed, which we must destroy. To achieve this we need to hit it twice with shots aimed at the centre of some field. When the tank gets hit it gets moved to a neighbouring field out of precaution. At least how many shots must we fire, so that the tank gets destroyed certainly?
We can neither see the tank, nor get any other feedback regarding its position.