100 Numerical Games Author:Pierre Berloquin Follow the hour hand and minute hand of a clock for 24 hours. How many times do they form a right angle? — Timothy's house has several rooms, each of which has an even number of doors, including doors that lead outside. Is the number of outside doors even or odd? — Stimulating and delightful, this collection of puzzles features original and classi... more »c brainteasers. The author, a puzzle columnist for Le Monde, specially selected these mind-benders for the widest possible audience, ensuring that they're neither too hard for those without a math background nor too easy for the mathematically adept. All puzzles are clearly stated and accurately answered at the back of the book ? and they're great fun to consider, whether you crack them or not. Includes a Foreword by Martin Gardner.« less