Before learning this lesson, students have some experience in expressing quantitative relations with line graphs and the knowledge base of solving problems with subtraction. As long as students can understand the meaning of the problem, it will be easy to solve it. Therefore, the teaching design of this lesson highlights the following three points: 1. Make full use of micro-lesson "Understanding automobile odometer" to help students understand the meaning of the question. The life experience of students in grade three is not very rich, and the taxi odometer is still unfamiliar to most students, so understanding the meaning of the problem is the key to solve it. In teaching, students are first arranged to watch the micro-lesson "Knowing automobile odometer" (which can be repeated) by using the activity class, so that students can have a preliminary understanding of automobile odometer, read the odometer and understand the meaning of the mileage displayed on the odometer as much as possible. 2. Guide students to cooperate and explore learning in class. Arrange students to discuss and communicate many times in teaching, pay attention to the communication situation and guide students to explore. Through the discussion and exchange of naughty odometer reading table, let students deepen their understanding of the quantitative relationship on the odometer; Through the discussion and exchange of the sketch of naughty lines, let the students find the method to calculate the mileage of taxis every day. 3. Consolidate and expand. Through practice, students are trained to solve mathematical problems related to odometer in real life.