Cut the Knot: Probability Riddles

Alexander Bogomolny

“So goes the story of Gordius, king of Phrygia, and his tight Knot. However, Alexander the Great simply sliced the Knot with his sword after many had tried and failed. He finally made it as far east as Northern India after conquering the majority of Asia.

Cut the Knot is a collection of probability puzzles designed to stretch the mind and improve logical and mathematical reasoning. These problems and their solutions were originally published on cut-the-knot.org and reflect the work of brilliant minds worldwide. Alexander Bogomolny will walk you through these chosen riddles following a thematic sequence. Before reading their solutions, give them a try. The non-trivial, unexpected solution might be just what you need, as it was for Alexander the Great.”