About the book: 2020 / Yakov Perelman's book "Puzzles and Entertainment" includes entertaining tasks, experiments, stories and games that help test your knowledge of mathematics and physics . Here you will find problems about clocks, number puzzles, games with matches and magic squares, the sum of the numbers of the sides of which surprised astrologers and alchemists of antiquity and, in their opinion, had magical properties. For middle school age.