There are three loops in a tangle of rope. How many are independent, and how many are interlocked? Two knights stand on a chessboard. How many other knights must you add so that each square is occupied or threatened by a knight? Among six seemingly identical drawings of mandalas, each rotated by multiples of 60 degrees, one is different. Which is it, and why? Challenge yourself with these mind-benders, brainteasers, and puzzles. Each of them has been carefully selected so that none will be too tough for anyone without a math background―but they're not too easy. Some are original, and all are clearly and accurately answered at the back of the book. Dover (2015) republication of the edition published by Charles Scribner's Sons, New York, 1976. See every Dover book in print at www.

doverpublications.com.