Compulsory education curriculum standard Beijing Normal University Edition Volume V, pages 44-45.

Second, teaching material analysis:

"What is perimeter" is the first lesson of Unit 5 "perimeter" in the first volume of the third grade of primary school mathematics published by Beijing Normal University. The main teaching content of this section is to understand the meaning of perimeter through practical activities such as drawing, measuring and touching, so as to pave the way for understanding the meaning of perimeter of various graphics and calculating perimeter in the future. Plan to teach a class.

The textbook of this lesson has the following characteristics: first, students can initially and intuitively understand the circumference of leaves by ants crawling around the edge of leaves; Then understand the meaning of perimeter through operation activities; Finally, through practical activities, let students further experience the close relationship between circumference and real life.

The method of "conversion" is an effective thinking method to study and solve mathematical problems. It is a way of thinking that uses the viewpoint of movement, change and development of things and the relationship between things to turn the unknown into the known and the complex into the simple. After-class exercises permeated the students with the mathematical thought of translation. Therefore, in teaching, we should try our best to combine the specific teaching content, infiltrate the idea of mathematical reduction, and consciously cultivate students to learn to solve problems with the idea of mathematical reduction, thus improving students' mathematical ability.

Third, the teaching objectives

1, knowledge and skills: know the perimeter by observing and calculating specific things or figures; Can measure and calculate the perimeter of triangle, rectangle, trapezoid and other graphics.

2. Process and method: cultivate the ability of independent thinking and hands-on operation in learning activities such as "painting and touching"; Cultivate the estimation ability in the process of estimating and measuring waist circumference, and further improve students' cooperation ability.

3. Emotion, attitude and values: combine specific situations to perceive the close relationship between the surroundings and real life.

Teaching emphasis: let students understand the meaning of perimeter in specific situations;

Teaching difficulties: can measure and calculate the perimeter of triangle, rectangle, trapezoid and other graphics.

Fourth, student analysis:

Grade three students have studied plane graphics. On the basis of students' existing knowledge and experience, new lessons are introduced by creating vivid and concrete situations to stimulate students' enthusiasm for learning. By drawing the edges of leaves and touching the edges of objects, students can experience the process of "doing mathematics". Pay attention to students' measurement experience by asking them to measure and calculate the perimeter of the surface they touch.

Five, teaching difficulties:

Teaching emphasis: let students understand the meaning of perimeter in specific situations;

Teaching difficulties: can measure and calculate the perimeter of triangle, rectangle, trapezoid and other graphics.

Teaching AIDS and learning tools for intransitive verbs;

Courseware, ruler, thread, tape measure, various objects, leaves, etc.

Seven, the teaching process:

(A), the creation of situations, the introduction of new lessons.

The teacher has just given leaves to each student, and today we learn knowledge with the help of leaves. Everyone will think, how can leaves help us learn knowledge? First, let's sketch it and draw its shape. How's it going? Is it like having an art class?

Take out a piece of paper, choose a favorite leaf, and draw its outline along the edge of the leaf with a colored pen.

2. Who will show you how to draw (please point with a pen and make it clear where to start and where to end)

3. What are the characteristics of what you just described? (The boundary line is drawn around the figure.)

4. Summary: It seems that no matter where we start, everyone draws a circle along the edge of the leaves (combined with physical demonstration). What should we call the length of this week? Can we give it a name (the perimeter of the leaf)?

The teacher also drew a leaf before class. Who can tell whether the teacher has drawn the perimeter of the leaves? (Show unsealed graphics)

What the teacher drew was not a closed figure without perimeter. What kind of figure has a perimeter?

The concept of perimeter is introduced, and the significance of perimeter is emphasized by combining closed graphics and unsealed graphics.

(2) Practice and exploration to learn new knowledge.

1, draw a picture in points, so that students can initially perceive the circumference.

Step 1: Use cai courseware to show multiple figures, so that students can classify the figures in comparison and reveal closed figures and non-closed figures.

Step 2: Ask the students to draw some closed figures they like.

Step 3: Show pictures to students selectively. Ask students to comment and point out the perimeter of the drawn figure, so that students can get satisfaction and further realize that the length of a closed figure in the same plane is called the perimeter of the figure.

2. Deeply perceive the meaning of the perimeter by searching and touching.

(1) With the above premise teaching, I ask students to do it: take out all kinds of blades prepared before class and draw the length of a week. In the process of painting, I realized that the perimeter is the length of a closed figure, but the inside part is not the perimeter. Then complete the textbook p45 1. (emphasizing sideline)

(2) Guide students to find the perimeter of the surface of the surrounding objects, such as the perimeter of the class schedule, the perimeter of the cover of the math book, the perimeter of the blackboard, the perimeter of the pencil box, etc. Touch, point and talk in the group.

(3) Put forward the mathematical problems in life: How does the length of a classroom go in a week? How to get around the playground?

(4) Know the perimeter of the plane figure. Talk: Just now we all meant the circumference of the surface of an object. Now let's look at the perimeter of the plane figure. What kind of graph is this (the courseware shows a triangle similar to p45 question 2, graph 1)? What is the circumference of this figure? The little black ant appreciates your judgment on him. It points out the perimeter of the triangle for us. Let's have a look. (dynamic demonstration, the little ant walks along the side of the triangle for a week. ) The length of a week that a small ant walks is the circumference of a triangle. Let's have some together.

(3), independent operation, consolidate new knowledge

1, measure the perimeter of a plane figure.

(1) Talk: We already know the perimeter of a plane figure, so how do we find the perimeter of a plane figure? Show the courseware one by one: question 2 on page 45.

Students open the second question on page 45 of the textbook. How do you want to measure a figure you like? Think and do with questions. For a figure surrounded by several line segments, measure the length of each side and add it up. We will do this in the future.

Step 2 measure the perimeter of the leaves

(1) Talk: We have measured the perimeter of the plane figure. You all have a leaf in your hand. So what is the perimeter of the leaves in your hand? Do you want to know how to get the perimeter of leaves? The study group can discuss it (Courseware plays light music)

(2) Students operate, teachers patrol and give guidance.

(3) class communication and collective comments.

Measure waist circumference

(1) girth is also widely used in life: for example, when making pants, the tailor should measure how long your waistline is in a week, which is usually called waistline.

(2) What is the estimated waist circumference of students?

According to this result, please estimate your waist circumference in centimeters.

(4) Consolidate exercises

(1) The courseware shows p45 Question 3: Graphics 1: These two graphics were originally two identical rectangles.

Cut out the first rectangle and fill in the second rectangle. Please compare their perimeters.

Please explain the reasons after the group discussion.

(2) The courseware shows p45 Question 3, Figure 2: These two figures were originally two identical rectangles. If the first figure is cut off, will the perimeters of the two figures be the same now?

(5) class summary

What did you learn in this lesson? Today, we know the perimeter and solve some problems with the knowledge of perimeter. Can you tell me how you feel?

(6), homework

Measure the perimeter of your desktop and bedroom floor.

Eight, blackboard design:

What is the perimeter?

Leaf surface circumference

Perimeter of closed figure

Nine, teaching reflection

In this class, students' interest is very high, and they have carried out full activities and independent exploration. In the full experience, they realized the practical significance of the circle. The teaching process is good, and the overall design embodies the educational concept of "from life to life".

1, I provide students with ample opportunities for practical activities, so that they can truly understand and master mathematical knowledge, mathematical ideas and methods, and at the same time gain rich experience in mathematical activities. The knowledge of "space and graphics" should pay more attention to students' direct experience in actual observation and operation. In this class, I let the students feel and get the concept of perimeter by themselves through a series of activities.

2. I create an open and free learning space for students, so that they can explore the unknown and solve practical problems by themselves in practical activities full of maneuverability, exploration and pleasure. The design of mathematical activities should pay attention to students' individual differences and personality characteristics. I let the students choose-choose the leaves and plane graphics you like; Choose the method you like to measure the circumference. Let every student be interested in the activities, and let the students experience the success or fun of learning in the activities that publicize their individuality, so as to increase their confidence in learning mathematics.

3. Good practical activities can make students actively cooperate and communicate. In this lesson, I designed two "measurements" to measure the perimeter of leaves and the waistlines of teachers and classmates. Students measure the perimeter of leaves themselves, but some students feel that their hands are not enough and ask their deskmates for help. They actively participate in activities, cooperate and communicate with each other. In such positive cooperation and communication, students' learning ability, practical ability and communication ability have been highly developed. They also help each other and learn from each other's strengths. Even students with learning difficulties don't find it difficult, and learning "circumference" is very easy.