MathDB
Problems
Contests
International Contests
APMO
2019 APMO
4
4
Part of
2019 APMO
Problems
(1)
Terrifying "2018 \times 2019" board
Source: APMO 2019 P4
6/11/2019
Consider a
2018
×
2019
2018 \times 2019
2018
×
2019
board with integers in each unit square. Two unit squares are said to be neighbours if they share a common edge. In each turn, you choose some unit squares. Then for each chosen unit square the average of all its neighbours is calculated. Finally, after these calculations are done, the number in each chosen unit square is replaced by the corresponding average. Is it always possible to make the numbers in all squares become the same after finitely many turns?
combinatorics
APMO