Teaching plan of "What is circumference" in the first volume of mathematics in grade three.

Teaching objectives:

1. We can know the circumference by observing, touching, tracing, measuring and calculating specific things or figures.

2. Perceive the close relationship between perimeter and real life in combination with specific situations.

3. Stimulate students' interest in learning mathematics and cultivate students' good mathematical emotional attitude.

Key points and difficulties:

Understand the perimeter and deeply understand the meaning of perimeter.

Teaching AIDS:

Courseware, ruler, various objects, cards.

Teaching process:

First, create a situation

Teacher: Students, two little ants were particularly disobedient last night. Their father punished them for running around the playground, but after one little ant ran, his father allowed him to rest, while the other was punished for running twice. Why? (Show the courseware).

Watch the animation of ants crawling on leaves (FLASH animation shows two ants crawling along the edge of leaves, one small ant crawling for a week and the other climbing halfway)

Teacher: Why does one little ant have a rest, but another little ant has to be punished for running away? How much did the remaining ant climb around the leaves, and the other one?

Answer by name and write on the blackboard according to the answer: the length of a week.

Teacher: Great! A small ant climbed a circle, that is, a week, and another small ant climbed half (the courseware shows the edge of the surrounding leaves)

Teacher: This "the length of a leaf a week" has a name. Do you know what it is called? (perimeter of leaves)

Teacher: Today we are going to learn what is the perimeter (blackboard writing).

Second, the exploration of autonomy and cooperation.

1, have a look

(1) When playing the courseware, the pencil draws a circle on the graph, and the length of the circle is the circumference of the graph.

(2) Play the courseware. Xiaoming runs around the playground. The length of Xiao Ming's running week is the circumference of the track.

Step 2 touch it

(1) Touch the edge of the leaf with your hand (emphasize where to start and where to end, the length of this week is the perimeter of the leaf. )

(2) Touch the edge of the cover of the math book. (emphasis: the length of this week is the circumference of the leaf surface. )

(3) Touch the edge of the class desktop. (emphasis: the length of this week is the circumference of the leaf surface. )

(4) Find the perimeter of the blackboard.

Teacher: Where is the circumference of the blackboard? Who can point it out?

Please point it out with a meter ruler all your life. The teacher will make a mark at the starting point of the students, and then mark it again when you return to the starting point.

(Design intention: Let students feel the edge of things in life, and initially feel that the circle should start from the starting point and finally return to the starting point. )

3. Draw the edge of the figure

Teacher: Look, are these two leaves beautiful? Do you want to follow the example of small ants and track their perimeter?

(1) Draw the perimeter of the leaves for students to demonstrate on the platform.

Please point with a pen and make it clear where to start and where to end.

(2) So, next, let's look at some children's sketches. Judgment: Which of the following pictures is correct? Why? (Show courseware)

(3) Teacher: Let's take out our favorite works and draw their borders with our favorite colors!

Group presentation.

(Design intention: Let students draw the edges of leaves, broaden their perceptual knowledge of perimeter, establish rich representations and initially understand the meaning of perimeter. )

4. practice.

The courseware shows the exercises and draws the edges of the picture below. (Note that the line segment inside the graph does not belong to the perimeter).

Third, deepen practice.

A closed figure has a perimeter.

Teacher: I have a triangular frame here. Where is its circumference?

Born on the stage, pointed out.

Teacher: If the teacher lets go of the connector, does this figure still have a perimeter? Let's think about it.

Health 1: I think there is a circumference.

Health 2: I don't think there is any circumference.

Teacher: We will have a debate in two groups. (divided into positive and negative sides)

Summary: Open graphics have no perimeter, only closed graphics have perimeter.

Fourth, the quiz-consolidate the application

1. Draw the edge of the picture below.

2. Identification: Which of the following figures have perimeters and which do not, and why? (Show courseware)