In "How long is the pencil?" Through activities such as estimation, measurement, discovery and thinking, students can explore knowledge, know decimeter and millimeter, experience and construct spatial concepts such as "1 decimeter" and "1 millimeter" and their relationship with other units. In the activity of experiencing the meaning of length unit, the students' answers are extremely wonderful. "Decimeter can be used to measure the length of a long object." "Millimeter is too small", "You can measure the length of a very short object". When experiencing the relationship among meters, decimeters and centimeters, students discussed that "1 0cm is 1 decimeter, and1decimeter is1meter".

This kind of teaching has activated the spark of students' thinking, deepened their understanding and knowledge of relevant mathematics knowledge, better mastered the effective learning methods of mathematics, enhanced their interest in learning mathematics and felt the joy of success.

Second, respect students' unique experiences and interpret their experiences and thoughts.

Students are the main body of mathematics activities, and experiential learning provides a good stage for each student's independent development. The development of students is different, so when students face new problems, they will look at the objective world from different angles and with different eyes. Their problem-solving process is a very personalized process.

In the teaching of how long a pencil is, after knowing 1 decimeter, ask a question, "Can you find 1 decimeter around you?" Perceive the length of 1 decimeter through the objects around you, respect students' unique experience, and appreciate their own way of experiencing and exploring the learning process. In such a dynamic classroom, students will flash different ideas at any time, patiently listen to each student's speech, encourage them to express their inner world, and interpret their experiences and thoughts from it, thus making the classroom full of vitality.