"What is circumference" is located in the first volume of the third grade mathematics textbook published by Beijing Normal University, pages 44-45. The specific teaching content is to know the circumference and cultivate the ability of observation, operation and cooperation. In specific situations, the close relationship between perception perimeter and real life is the focus and difficulty of this class.

"What is perimeter" is the first section of this unit, which is based on students' understanding of triangle, parallelogram, rectangle and square. It is mainly to understand the concept of perimeter, form and establish a preliminary cognition, and lay the foundation for learning the calculation of perimeter of plane graphics. Let students be in a leading position in observation and hands-on operation, organize students to watch and do it, encourage students to discuss and communicate with each other, and inspire students to think and summarize positively. In short, we should try our best to create enough time and space for students to play and explore. On the basis of * * * knowledge, we should establish mathematical models and acquire new knowledge.

Junior three students are curious, used to thinking in images, have certain observation and operation ability, and can master the knowledge of this lesson from activities.

Integrated thinking

Mathematics activities should not only pay attention to the results, but also pay attention to whether students actively participate in the activities, whether they are willing to cooperate and communicate, feel the fun of cooperative learning, and enhance their awareness of applied mathematics. Therefore, in the process of situation creation, new knowledge learning and knowledge application, this course effectively uses multimedia-assisted teaching. The specific application is as follows:

In the process of creating situations and stimulating interest, the animation plot of small ants crawling through leaves is displayed, which fully mobilizes the enthusiasm of students and achieves the interesting effect at the beginning of class. The first question in the 45-page exercise of the presentation textbook is to provide opportunities and take the initiative to participate in this link. After students draw the perimeter of these figures, they will add some pictures that students are interested in in in their daily life, encourage students to draw the perimeter of these figures, and let them have an independent thinking and naturally transition to the later teaching process. In the process of actual measurement and deepening understanding, the courseware inspires students to calculate the perimeter of these figures by showing rectangles, triangles, squares and trapezoid, so that students can further understand the meaning of perimeter. In the game of breaking through obstacles and consolidating cognition, the courseware shows the third question on page 45 of the textbook, allowing students to discuss in groups whether the perimeters of the two figures in each small question are the same, encouraging students to express in their own language, and constantly improving and deepening their understanding through mutual complement.

Teaching design

(1) Teaching objectives

① Establish the concept of perimeter.

② Let students "move" and experience the process of "doing mathematics" through activities such as observation and operation.

③ Cultivate students' habit of observation and thinking, so as to achieve the purpose of independent inquiry learning, active participation in learning and cooperative exchange learning.

(2) Teaching emphasis

Understand the surroundings and cultivate the ability of observation, hands-on operation and cooperation.

(3) Teaching difficulties

In a specific situation, the perceptual perimeter is closely related to real life.

(4) Preparation before class

Teaching courseware computer TV watercolor pen ruler rope

(5) Teaching process

teaching process

Design ideas and multimedia application analysis

(A) create a situation to stimulate interest

One day, the little ant came to a primary school to see how the pupils had a math class. The teacher gave it a leaf ... look at the big screen and see how it makes friends with the leaf.

Courseware demonstration: an animated plot of a small ant crawling on the leaves for a week.

Guide observation and establish cognition: (pointing to the route that the little ant walked in the picture) How did the little ant walk? Can you "point" with your fingers along the outline of a math textbook like a little ant?

(b) Provide opportunities for active participation.

1, draw, draw.

Draw a picture: Are you interested in your favorite leaves?

Draw a line: the edge of this leaf, ok?

(Students do it by hand)

Thinking: What are you going to do?

Tip: think while painting, where to start painting and where to finish painting?

(After painting, show the method of drawing the sideline with courseware animation. )

Question: Where do you think the perimeter of this leaf refers to?

The little ant said (courseware realization): "The length of the week I climbed is the perimeter of the leaves." Which key word in his words impressed you deeply?

Transition: You can draw leaves for a week, and you can certainly draw the following picture for a week.

Courseware demonstration: practice the 45-page 1 question and add some pictures, such as

Comparison: Who can draw fast and well? Draw a week of these numbers by the way we just drew a week of leaves? Let's start. ...

The students begin to draw the boundaries of the figure. After painting, demonstrate the dynamic process of drawing the sideline with courseware. )

Try it and say it.

Guided observation: drawn graphic edges

Touch: a sideline of math textbooks for a week.

Try it: give these sideline businesses a name?

Students express their opinions.

Choice: Which is more accurate? (Show of hands)

Refer to the selection results, guide the analysis and determine the concept (perimeter).

Student Example: Find an example from us to illustrate what perimeter is. ...

Say: What is the circumference of a figure? Let different students express themselves in their own language according to their own understanding.

3. Debate and discussion

Demonstration: Fold a wire into a triangular frame.

Say: where is its circumference?

Name the students and ask them to point it out on stage.

Demonstration: Let go of the connector.

Q: Does this figure have a perimeter?

group discussion

Delegates report the discussion results and briefly explain the reasons (team members are encouraged to add)

Summary: Open graphics have no perimeter, only closed graphics have perimeter. Name the students and write them on the blackboard. Read them twice. )

List: Among the familiar figures, which ones have perimeters and which ones don't?

(C) the actual measurement, deepen understanding

1, measure a quantity

We drew it just now and touched the perimeter. It seems that the perimeter is in our life. For example, when making pants, the tailor should measure the length of the waist, that is, the waist.

Guess: the teacher's waist circumference, who has the best eyesight? (Name the students' blackboard writing records)

Some students demonstrated the measurement process, and the teacher instructed the method in time.

Estimate: Your waistline.

Measure: Are you sure?

2. Do the math problem (exercise the second question on page 45)

Courseware demonstration:

Calculation: The perimeter of these geometric figures.

Say: What is the circumference of a triangle? What are the perimeters of rectangles and trapezoid?

Inspiration: What did you find?

Induction: Add the lengths of each side of the graph to get the circumference of the graph.

(4) The game of breaking through the customs, to consolidate the understanding that everyone has initially perceived what the perimeter is. Would you like to participate in the game of "breaking through the three customs"? (Courseware shows 45 pages to practice the third question)

Discuss in groups: Are the perimeters of the two figures in each question the same?

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(5) Improve understanding and summarize in class.

Let's talk about it What is your biggest gain from this course? What have you learned? What else don't you understand?

Introducing animation into this class is exactly what students like, fully arousing their enthusiasm and giving the whole class a good start. By observing the process of ants climbing leaves three times, students can clearly distinguish what a complete week is, paving the way for understanding the perimeter later.

Stimulating students' interest in learning is the premise of guiding students to actively participate in the learning process. The application of multimedia courseware demonstration can guide students to pay attention from unintentional to intentional, thus stimulating students' urgent desire to explore the unknown.

It creates opportunities for students to actively participate in mathematics teaching activities, so that children can feel the meaning of perimeter in the process of independent thinking, hands-on operation and communication with others, and change "teachers teach and students accept" into "independent discovery and * * * communication", and feel the fun of exploring mathematics problems in activities.

Guide to experience the length of a graphic week.

Help students further master the correct method of drawing boundary lines.

Illustrated pictures and sounds help to deepen students' memory.

Give students a process of independent thinking and make a smooth transition to the later activities.

Encourage students to actively participate.

Modify and correct errors, reach the knowledge of * * *, and understand the perimeter of basic graphics.

Mobilize students' active participation and reflect the democratization of classroom activities.

Encourage students to observe life from the perspective of mathematics, find mathematics in life and feel the close relationship between mathematics and life.

Through debate and analysis, it is clear that the specific object of the perimeter is a closed figure.

Inspire thinking.

Deepen cognition in communication.

To cultivate students, we should not only "know why" but also "know why".

Draw inferences from others and deepen understanding.

Through practical activities such as measurement and calculation, students can further understand the meaning and application of perimeter. Teachers guide students to find problems on their own initiative, explore methods independently, initially feel the application value of mathematics, give play to the effectiveness of group cooperation, and let children do their best. Students feel that there is mathematics everywhere in their lives, and they can apply what they have learned in class to solving practical problems.

Children's wisdom comes from their fingertips. In dynamic practical activities, children can actively transform the abstract knowledge they have learned into "real understanding".

Self-test, master measurement methods

Encourage students to express in their own language and complement each other, so as to improve and deepen their understanding.

The timely playing of multimedia courseware turns static into dynamic, which effectively breaks through the difficulty of the perimeter of combined graphics.

Let the students express their opinions and give them an opportunity to sort out their knowledge. Through suggestive guidance, let the students sum up what the perimeter is, supplement the blackboard writing, improve the content and experience the fun of success.

Blackboard design: