This book is the founder of the genre of scientific and entertaining literature, the Russian scientist Ya. and . Perelman combines two works of the author: "Entertaining Mathematics" and "Entertaining Arithmetic" It aims to instill in its reader a taste for the study of mathematics, to arouse his interest in independent creative pursuits and to introduce him to the world of scientific knowledge. The book contains fascinating stories-tasks with unusual plots on mathematical topics, curious examples from everyday life, puzzles, humorous questions and experiences - and all this through the game, easily and at ease. The formulation of problems, their arithmetic and logical methods of solutions and the conclusions arising from the solutions will arouse interest not only among young novice mathematicians familiar only with the elements of arithmetic, but also among readers who are well versed in mathematics. The author's style of writing corresponds to the 20th years of the twentieth century and is preserved unchanged.