275

Part of 1979 All Soviet Union Mathematical Olympiad

Problems(1)

ASU 275 All Soviet Union MO 1979 checkers in chessboard

Source:

What is the least possible number of the checkers being required
a) for the

8\times 8

chess-board,
b) for the

n\times n

chess-board,
to provide the property:
Every line (of the chess-board fields) parallel to the side or diagonal is occupied by at least one checker ?

Chessboardminimumcombinatorics