Textbook in PDF format This book is a collection of 57 very challenging math problems with detailed solutions. It is written for anyone who enjoys pondering difficult problems for great lengths of time. They are divided into four categories: General, Geometry, Probability, and Foundational, with the Probability section constituting roughly half the book. Many of the solutions contain extensions/variations of the given problems. In addition to the full solution, each problem comes with a hint. For the most part, algebra is the only formal prerequisite, although a few problems require calculus. Are you eager to tackle the Birthday Problem, Simpson’s Paradox, the Game-Show Problem, the Boy/Girl Problem, the Hotel Problem, and of course the Green-Eyed Dragons ? If so, this book is for you ! You are encouraged to peruse the problems via either the Look Inside feature on Amazon, or the author's Harvard webpage (where all of the problems are posted), to gauge whether the level of difficulty is right for you