In mathematics classroom teaching, the principle of layered practice is to teach students in accordance with their aptitude, step by step, but there is no regulation, and appropriate is the best. Generally speaking, there are three levels of ability: low, medium and high. Each ability level can be divided into three difficulty levels: A, B and C. If an exercise paper of each ability level is calculated as 100, and 70% to 80% of students get 70% to 80%, it is considered as an excellent design. (I call myself the 78 principle) If an exercise paper is calculated according to 100, it will be divided into three grades: A, B and C according to the degree of difficulty. The proportion of questions is 7:2: 1 or 8: 1: 1, that is, Class A accounts for 70% to 80% (that is, the 78 principle). In short, it depends on the study. You can ask the question "What levels of exercises are appropriate in mathematics classroom teaching", which shows that you have thought about exams from the perspective of students' learning and learning effectiveness, and you will definitely become an excellent teacher popular with students!