Question 2
A Berukone board is a square grid of circles, some containing numbers. Connect equal-numbered circles by paths through unnumbered circles, following the grid links. Each numbered circle must have exactly one selected incident link and each unnumbered circle at most two. Here are a solvable board and an impossible board.
How many of the following four boards cannot be solved?
Board 1:
Board 2:
Board 3:
Board 4:
How many of the following four boards cannot be solved?
Board 1:
Board 2:
Board 3:
Board 4: