The puzzle is thus: You place a 2×2. Each time you move the 2×2 square you change the colors in the following:
- The whole 3×3 starts off grey.
- Within the 2×2 grey goes to blue, blue goes to yellow, yellow goes to grey
A sequence of moves were made that resulted in the 3×3 with the question marks in it. Which of the multiple choices below it is a viable possibility to fill in the squares with question marks?
- Original Vestibular Exam here
- My Markup of the Exam here
- My Brute Force Solution
- Olimpiada Brasileira de Matematica Escola Publica – from various years.
Solution of the puzzle by a much more direct route from the OBMEP