Rook race to the far corner of a chessboard
Question
A rook starts in the bottom-right square of an board. Two players alternate moving it any number of squares, but only upward or leftward. Whoever puts it on the top-left square wins. Should you move first or second to be certain of winning? Answer or .
Short answer
. The rook starts on the diagonal joining the two corners (equal distance up and left). Any move leaves that diagonal, and the second player can always move back onto it, finally reaching the corner. It is two-pile Nim with equal piles.
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Open the worked solutionLessons behind this question
- Sample Spaces, Events, and the Probability Axioms
- Conditional Probability, Total Probability, and Bayes' Rule
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