25 coins on 16x16 board
Source: XIV May Olympiad (Olimpiada de Mayo) 2008 L1 P5
September 22, 2022
combinatorics
Problem Statement
On a board, coins are placed, as in the figure. It is allowed to select rows and columns and remove from the board all the coins that are in those lines. Determine if it is possible to remove all coins from the board.
https://cdn.artofproblemsolving.com/attachments/1/5/e2c7379a6f47e2e8b8c9b989b85b96454a38e1.gif
If the answer is yes, indicate the rows and columns selected, and if no, explain why.