LR1

Part of 2016 Costa Rica - Final Round

Problems(1)

21 tiles, some white and some black, in a 3 x 7 rectangle

Source: OLCOMA Costa Rica National Olympiad, Final Round, 2016 Shortlist LR1 day1 (logical reasoning)

21

tiles, some white and some black, a

3 \times 7

rectangle is formed. Show that there are always four tokens of the same color located at the vertices of a rectangle.

combinatoricstilesrectangle