Rooks on a 8 by 8 checker board. Probability problem

probability

Place the first rook. No matter where it is placed, it attacks $2\cdot 7 = 14$ squares of the chessboard. Because both pieces are rooks, if one attacks the other, they both attack each other.

This means that $\dfrac{63-14}{63} = \dfrac{7}{9}$ places on the chessboard are safe for the other rook such that they won't attack eachother.

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