The book is an addition to the mathematics textbook and is intended for schoolchildren in grades 5-6 and their teachers. It includes various tasks for compiling expressions, finding numbers, cutting figures into equal parts, puzzles, numerical puzzles, joke problems, etc. There are simple problems, but there are also those when solving which you need to be smart. Some tasks at the end of the book are answered, others are just tips to help find a solution. This collection includes problems from various books on entertaining mathematics, from the magazine "Quantum" and problems invented by the authors. There are also problems proposed at mathematical olympiads.