All task books are based solely on trusted international sources on which our Asian colleagues have been working for over 20 years (Taiwan, Japan, Korea, China).
All training is divided into levels according to the international classification, at the completion of each level by a student, the instructor must clearly know and track the emerging and entrenched skills. This is one of the most important stages in the training of mental arithmetic, since today the vast majority of teachers do not own this information along with a clear technique for working on abacus.
We really want to increase the level of mental arithmetic of students and teachers, and this is impossible without observing the criteria for counting.
All textbooks are divided into 12 levels, where 12 and 11 are the study and development of formulas. Starting from level 10, there is an improvement and development of counting skills on the abacus and, further, mental. Each manual necessarily includes practice on an abacus, preparation for certification (its samples), a mental account, as well as answers to all blocks!