1, numerical range: cards are grouped according to the numerical range involved in oral calculation questions. For example, one group can contain questions between 0- 10, another group can contain questions between 10-20, and the third group can contain more than 20 questions.

2. Themes or concepts: grouping according to mathematical themes or concepts involved in oral calculation, for example, one group can be basic four arithmetic problems, another group is fractional arithmetic problems, and the third group is geometry problems.

3. Learning stage: Students are grouped according to their grades or language ability. One group can be suitable for beginners, another group is suitable for intermediate and the third group is suitable for advanced.