1. Create situations and provide materials.

Through the communication before class, I know more about our school. Do you want to see the school where the teacher is? The teacher will be happy to introduce you. The teacher took a group of photos of our school before coming. Let's enjoy it together

Multimedia Presentation of Campus Pictures and Textbooks Page 64 Information Window 1:

Look, how beautiful these flower beds are. Which flower bed do you like?

Oh, some students like rectangular flower beds; Others like square flower beds; And those who like fan-shaped flower beds.

The students of the campus green team also like these flower beds. They want to protect the flowers and plants in the flower beds. Any good suggestions?

Well, you want to put a guardrail on the flower bed. That's a good idea!

The students of the green team want to go with the big man. They also plan to install guardrails on each flower bed.

For the convenience of research, the teacher made rectangular, square and fan-shaped flower beds into graphic cards according to a certain proportion. Please point out in the group where the guardrail of each flower bed card should be installed.

Where do you think the guardrail is suitable? Can someone show you?

Who wants to say on behalf of your family where the guardrail of the flower bed should be installed?

Well, it is installed outside the flower bed; Do you agree with him? It seems that your group just discussed it seriously. Summary: Students, in mathematics, the circle around the outside of the figure is called a week.

Dialogue: Who will draw the round cards in the week?

Follow-up: Is this a week? Where to start? Where does it end?

(Well, that's very clear), starting from a point and ending at this point.

Please choose a card you like in the group and draw it with a colored pen for a week.

Somebody show me.

Follow-up: You chose a rectangular flower bed. Can you tell me how you draw it? Does everyone understand what he said?

He started from this point, followed the edge of the rectangle and finally returned to this point. You made it very clear. Do our classmates understand? )

Do you have any other graphics? Who will say something?

You start from a point on the side of a square, trace along its side, and finally return to this point (the voice of answering questions is really loud)

Who can tell me where the fan-shaped flower bed week is? Since there are so many students to answer, let's listen at the same table and pay attention to the integrity of the words.

(The picture shows three flower beds tracked for a week. Please look at the screen. A week of a graph starts from a point on the edge of the graph, along the edge of the graph, and then returns to this point.

Third, with the help of materials, sum up the concept (1) and talk about it to understand the length of a graphic week.

Talk: How long does it take for each flower bed? What do we need to know to solve this problem?

Yes, our classmates are really smart. Just know the length of the flower bed in one week.

Board post: How long does it take for each flower bed?

Blackboard: The length of a week.

Follow-up: How can I know the length of these flower beds in a week? Please choose one or two pictures for each group. Students think for themselves first, and then share your thoughts with the students in the group.

1. Who said how to measure the length of a rectangular flower bed?

This classmate said to use pace. Walk along the edge of the flower bed and estimate the length of the flower bed for one week. Well, any other ideas? )

For you, measure the edge of the flower bed with a tape measure. Your method is not bad either. )

Is there any other way? Measure the four sides of a rectangle and add them up. You are really a smart classmate. )

2. How to measure the length of a square flower bed in a week?

Is there any other way besides the pace and tape measure just mentioned?

You tell me, oh, just measure the length of one side and add them up, and you can calculate the length of a square flower bed in one week. This method of yours is wonderful, which can let us know the length of a square in a short time.

3. Excuse me, what's a good method for the length of a fan-shaped flower bed?

For you, just measure the lengths of two straight edges and 1 curved edges respectively, and then add them up. Do the students agree with his method? This method of yours is also very good, and it is very clear. )

4. How to measure the length of a round flower bed?

(1) pace. Walk along the edge of the flower bed and estimate the length of the flower bed for one week.

② Measure the periphery of the flower bed with a tape measure.

(3) From a point on the edge of the circle, measure a circle around the edge of the flower bed with a line, then return to the origin, and then measure the length of the line to get the length of the round flower bed. Do you understand what he said? Well, your measurement method is also very good)

The old teacher thinks that the students in our class can really use their brains to think, and they can come up with so many methods at once, and the length of a figure can be measured in one week. Teachers should also learn from you!

(2) Compare the definitions of derivation perimeter.

Please look at these two cards. Whose circumference is it? You tell me.

It seems that the circumference of the surface of an object is long and short, and the length of the surface of an object is the circumference.

Blackboard writing: perimeter

Chessboard title: Know the circumference

(3) Find out and further perceive the meaning of perimeter.

Dialogue: Can you find out the circumference of the object around us and estimate its circumference?

Who will talk about your findings? The circumference of the table is about 150 cm.

The cover circumference of this math book is about 80 cm.

Anything else? The perimeter of the window glass is about 4 meters.

Students really have a pair of eyes that are good at discovering.

Write on the blackboard: Know the circumference

The length of a circle on the surface of an object is called the circumference.