A square is divided into 25 cells. Initially all its cells are white, as shown.
Neighbouring cells are those that share a common edge. On each move two neighbouring cells have their colours changed to the opposite colour (white cells become black and black ones become white).
What is the minimum number of moves required in order to obtain the chess-like colouring shown on the right?
Select one option, then click Submit.
11
12
13
14
15
Select an option, then submit.
Sign in or create an account to reveal answers, view the solution, and save your progress. Create a free account to unlock practice and keep track of your work.
Pink Kangaroo 2016 (2016)
One puzzle per day. Cryptarithm, Magic Square, Summit. No sign-up required to play.
Play daily puzzle →Interactive problems and curated lessons—water pouring, magic squares, knight's tour, and more.
Browse library →See how you rank. Top solvers by problems solved correctly. Sign in to climb the ranks.
View leaderboard →Pink Kangaroo 2016 (2016)