This part of the content is based on students' study of plane figures such as triangles, parallelograms, rectangles and squares, and it is also the basis for further study of perimeter calculation of plane figures. This lesson plays a connecting role in the study of "spatial graphics" in primary school mathematics.

Analysis of learning situation:

"Perimeter" is abstract for junior three children, because in real life experience, students see, touch and use more shapes and sizes of graphics, but pay less attention to the feeling and attention to perimeter. In order to improve students' interest in learning and give full play to their main role, textbooks are introduced from familiar life scenes, which is in line with students' acceptance psychology.

Teaching objectives:

Knowledge and skills: By observing and operating specific scenes, people and objects, we can know the perimeter and understand its meaning. And can measure and calculate the perimeter of simple graphics.

Mathematical thinking: through the process of observation, measurement and other mathematical activities, students can develop the concept of space while gaining intuitive experience.

Problem solving: In learning activities, different strategies can be used to solve problems, which reflects the diversity of problem solving methods.

Emotion and attitude: Perceive the close relationship between perimeter and real life, and stimulate students' interest in learning mathematics.

Teaching emphases and difficulties:

Know the perimeter, understand the meaning of perimeter, and develop the concept of space.

Instructional design:

(1) Take a look and draw a picture.

1. Students, what season is it? Autumn is the season when leaves fall. The teacher brought some beautiful pictures of leaves to the students! What beautiful leaves! The lovely ant is very happy to see it! It says it can draw leaves, and it can draw beautiful leaves with one stroke! Look! (Show the courseware) Look carefully at how two little ants draw. Who draws well?

Teacher: Start from a point and then go back to the starting point. Mathematically, it's called a week. This outer edge is called the sideline.

Teacher: Draw a circle along the edge of the leaf, and a beautiful leaf pattern will appear. Now, who can tell us how ants draw?

Health: The little ant drew a circle along the edge of the leaf and finally returned to the starting point.

Teacher: Little ants can also be teachers. They taught us to draw beautiful leaves. Have you learned?

Please take out a piece of paper, choose a favorite leaf, and draw its outline along the edge of the leaf with a colored pen. Let's start!

2. all right! Who wants to show you how to draw? Please point with a pen and make it clear where to start and where to end. )