Pierre Berloquin 
100 Geometric Games 

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.