This book is an attempt to systematically outline arithmetic within the program of classes V and VI. Thus, it is assumed that our reader knows mathematics within elementary school: he knows how to perform arithmetic operations with natural numbers and even has some idea of ​ ​ fractions. School arithmetic material is presented in the book systematically, so the sequence of presentation differs from that adopted in well-known textbooks in mathematics for grades 5-6. The main exercises and tasks are given. For teachers of mathematics and self-education. Available to students in grades 5-6.