MathDB

1

Part of 2017 Serbia JBMO TST

Problems(1)

Combinatorics with grid

Source: Serbia JBMO TST 2017

3/8/2020
15 of the cells of a chessboard 8x8 are chosen. We draw the segments which unite the centers of every two of the chosen squares. Prove that among these segments there are four segments which have the same length.
combinatorics