"Curriculum Standard" points out: "Effective mathematics learning activities cannot rely on simple imitation and memory, and hands-on practice, independent exploration and cooperative communication are important ways for students to learn mathematics". In the process of mathematics teaching, we should pay attention to learning and understanding mathematics from students' life experience and existing knowledge. Therefore, in the teaching of How Long is a Pencil, I try my best to provide students with familiar situations and closely link measurement with students' practical activities, so that students can learn while doing. Make full use of students' existing knowledge, experience and familiar things to organize teaching, so that life can truly become the source of mathematics knowledge and learning mathematics can truly meet the needs of students' life; At the same time, broaden the channels of applying mathematical knowledge and cultivate students' ability to analyze and solve practical problems.
In the teaching of how long a pencil is, I first ask students to recall the two length units of meter and centimeter they learned in grade one. Let them say what English letters are used for meters and centimeters respectively, and use gestures to indicate the lengths of 1 meter and 1 centimeter, and then talk about the relationship between meters and centimeters. Then, create a situation to estimate and measure the pencil length, and derive the unit of decimeter and the relationship between meter, decimeter and centimeter. I prepared four pencils about 10 cm long before class, and asked them to estimate the length of the pencils in the group first, then make actual measurements and report to the group. This is also the first cooperation point of this course. When the students say that the measurement result is 10 cm, I will directly tell them that 10 cm is 1 decimeter, and let them see how long 1 decimeter is. Then let the students indicate the length of 1 decimeter with their hands and draw 1 decimeter with a pencil. Finally, according to the students' existing knowledge: 1 m = 100 cm, 1 m = 10 decimeter is deduced.
The second cooperation point of this lesson is to know how long 1mm is. I also ask students to make an estimate in the group before measuring the length of the eraser. When the students measured that the rubber was a little more than 6 cm, I said, "A little more, can you express it with a specific number?" "Yes!" The students scrambled to answer. At this time, I took the opportunity to guide students to observe how many cells are in 1 cm. When the students say 10 cm, I introduce each cell to the students as 1 mm, so that we can get 1 cm = 10 mm. Through group cooperation and communication, I have learned about millimeters and mastered the relationship between centimeters and millimeters.
In order to deepen students' understanding of 1 decimeter and 1 millimeter, I asked students to actually measure the length, width and height of their favorite objects in life. Some students measured the length, width and height of a math book. Some people measure the length, width and height of their pencil cases, while others measure the thickness of coins. They can not only measure accurately, but also use the length unit properly, which further deepens the perceptual understanding of the length unit and makes the application of the length unit more flexible.
Through this lesson, I guide students to connect what they have learned and apply it to real life, which can make what they have learned continue, expand and extend, promote students' awareness of exploring and discovering problems, and cultivate students' preliminary practical ability and spatial concept. Students get a pleasant emotional experience in hands-on operation, so that students can really feel mathematics and experience mathematics.