The content of inverse proportion is the deepening of the previous proportional knowledge such as "variable" and "positive proportion", and it is the basis for learning functions in the future. It has the function of connecting the past with the future and is an important content in the teaching of proportional preparation knowledge in primary schools.

Second, the teaching objectives

According to the "New Curriculum Reform Standard" and the intention of arranging primary school mathematics textbooks, I have determined the following teaching objectives:

1, cognitive goal: to understand and master the meaning of inverse ratio by perceiving examples in life, and to preliminarily judge whether two related quantities are inverse ratio.

2. Ability goal: Students develop the ability of observation, thinking, comparison, induction and summary in interactive and exploratory cooperation and exchange activities.

3. Emotional goal: Let students feel the extensive application of inverse relationship in life in the process of independent inquiry and cooperation and communication.

Third, teaching focuses on difficulties.

Teaching emphasis: understand the meaning of inverse proportion.

Teaching difficulty: master the method of judging whether two quantities are inversely proportional.

Fourth, the teaching process

Based on the above analysis and assumptions, I will conduct classroom teaching according to the following links:

(A) the story import, guide the topic:

Tell the story of the rich and the hat and lead to a new lesson.

If the total amount of cloth is fixed, how will the amount of cloth used in each hat change with the number of hats, and what is the law of the change? What is the relationship between these two quantities? (blackboard title: inverse proportion)

(Design purpose: Introduce the topic with stories, so that students can initially feel the meaning of inverse proportion through stories and stimulate their interest in learning. )

(2) Teachers' guidance and independent inquiry:

1, the courseware shows "addition table" and "multiplication table", knowing the straight line with 12 in the addition table and the curve with 12 in the multiplication table. Understand the difference between the two quantities through preliminary perception.

Question: Are these two quantities inversely proportional to what we learned today? This question will be answered later. Students, look at the following questions first.

Uncle Wang is going to visit the Great Wall. The time required for different modes of transportation is as follows. Please complete the form below.

[hint]

A.tell me what your results are based on.

B.how do you observe the changes of speed and time?

C.what else did you find?

Let the students talk at the same table first, and then call the students to answer the discussion results. Blackboard writing speed × time = distance (certain)

3. Show the situation of "juice separation"

Please finish this problem by yourself according to the method just now and think about you carefully.

What did you find? After observation and thinking, students discuss in groups: the total amount of juice remains unchanged. When the number of cups changes, does the amount of juice allocated to each cup change? What is the law of change?

The blackboard says: the amount of juice per cup × the number of cups per minute = the total amount of juice (certain)

4. Group discussion summarizes the significance of inverse proportion.

(1) summarizes the similarities between Example 2 and Example 3.

Question: Please compare Example 2 and Example 3, and say what are the similarities between these two examples?

(2) Summarize the meaning of inverse proportion and the judgment method of inverse proportion.

5. Discuss whether "addition table" and "multiplication table" are inversely proportional.

6. Use what you have learned to judge whether the story of the rich and the hat is inversely proportional.

(Design intention: By observing the specific situation, let the students sum up the concept of inverse ratio and the method to judge whether the two quantities are inverse ratio on the basis of thinking, cooperation and comparison. Finally, the relationship between addition table and multiplication table is analyzed and discussed, and the problems raised at the beginning are solved.

Consolidate the teaching content of this lesson. )

(3) Consolidate exercises

1. Judge whether the two quantities in each of the following questions are inversely proportional, and explain the reasons: (Answer by name)

(1) The height of the high jump and her height.

(2) The unit price of apples is fixed, and the quantity and total price of apples are purchased.

(3) The speed and time required for Uncle Zhang to ride his bike from home to the county seat.

(4) The total amount of coal burned is certain, the amount of coal burned every day and the number of days that can be burned.

(5) The total production of TV sets is fixed, the number of TV sets produced every day and the number of days required.

2. Find out what other examples of inverse proportion exist in life.

(design intent: use the knowledge of positive and negative proportions to judge through exercises.

Whether these two quantities are in direct proportion further deepens students' understanding of inverse ratio and consolidates the relevant knowledge of direct ratio. Finally, through the link of finding, let students feel the wide application of inverse proportion in life. )

(4) class summary

What did you learn from this course? Tell everyone what you've gained. in life

There are many examples of inverse proportion in the book. Please observe them carefully in your life.

(Design intention: Let students reflect on what they have learned in this class and tell their classmates what they have gained. This process is a process of knowledge reproduction and a process of re-learning and consolidation. )

Five, the blackboard design:

proportion

Speed × time = distance (certain)

The amount of juice per cup × the number of cups per minute = the total amount of juice (certain)