Mental maths

This manual includes all possible combinations of single and double digits at the level "SIMPLE (addition). The collection contains more than 700 examples (10 options), divided into sections according to the composition of numbers. The manual is designed to solve examples of mental arithmetic at the "SIMPLE level on the abacus and mentally. It is recommended to use both for self-development of the acquired counting skills, and in preparation for classes and tests in mental arithmetic.