Question 32
A piece is placed at the center of every square of a $5\times5$ board. A piece may move only to a square sharing exactly one vertex with its current square, as shown below. Several pieces may occupy one square and a square may remain empty. At a certain moment, all pieces move simultaneously.
a) Give a set of moves for the 25 pieces that leaves exactly 5 empty squares.
b) What is the minimum possible number of empty squares afterward?
a) Give a set of moves for the 25 pieces that leaves exactly 5 empty squares.
b) What is the minimum possible number of empty squares afterward?