There are two examples in the textbook for teaching. Example 4 is a common problem in teaching. First, the distance between Wang Hong and other three people is represented by a histogram, so that students can not only know how many kilometers each person runs, but also recall old knowledge and intuitively feel the numbers related to scores in the picture, providing experience for solving the problem that "one number is a few percent of another number"; Then guide students to link the question "How far Li Fang runs is Wang Hong's" and "How far Li Fang runs is Wang Hong's", so that students can transfer their existing problem-solving experience to new problem situations; Finally, the textbook guides the calculation skills of finding percentage. Write the quotient in decimal form first, and then rewrite the decimal into percentage, so that students can understand the simplicity of expressing the result of division with decimal. Example 5 Practical problems of finding percentage in teaching. The textbook first helps students understand that "attendance is the percentage of actual attendance to the number of people who should attend", and explains that seeking percentage is the percentage of one number to another. After calculating the attendance of the track and field team on Monday, let the students choose the data of two days to calculate the attendance, and consolidate their understanding of the attendance. On this basis, the textbook allows students to ask questions about the survival rate of saplings and tell examples of percentage in life, so that students can further understand the meaning of percentage and feel the wide application of percentage in life and production.
The teaching focus of this lesson is to understand and master the idea and method of "what percentage of one number is another number". The difficulty is to analyze the quantitative relationship and find the correct unit "1".
[Teaching objectives]
1. Through the transfer of knowledge, let students understand the idea of solving the application problem "What percentage is a number" and master the calculation method of percentage.
2. In the process of solving practical problems, we can further understand the internal relationship between mathematical knowledge, thus being inspired by the dialectical materialism view that there is a universal relationship between things.
3. Understand the application of percentage in specific life problems, stimulate students' enthusiasm for learning, and further establish confidence in learning mathematics well.
[Teaching process]
First, pave the way for pregnancy
1. What is a percentage?
2. Rewrite the following figures into percentages.
0.6 7/ 10 3.5 5/8 1
3. Give the statistical chart of Example 4, and observe carefully to get information.
(1) Compare the multiple relation of any two quantities, and put forward the question "A fraction of one number is a fraction of another number". How should I ask this question?
How far does Li Fang run than Wang Hong?
How far does Wang Hong run than Lin Xiaogang?
……
(2) Free oral answers and timely questions: Who is better than who? Who is this unit "1"?
(3) Summary: How to find the score of one number to another?
4. These questions all express the multiple relationship between two people's running distance and scores. Percentages also represent multiples. Can you change "what percentage of a number is another number" to "what percentage of a number is another number"?
In this lesson, we will learn to solve a simple practical problem: what percentage is one number in another?
[Comment: According to the law of knowledge transfer, we should review the meaning of percentage at the beginning of class, and the method of converting fractions and decimals into percentages, focusing on the problem-solving method of "the fraction of one number is a fraction of another number", paving the way for the smooth exploration of new knowledge and the transition to new courses. ]
2. Explore new knowledge
(1) Teaching Example 4: Find what percentage of one number is another.
1. Change the review question "What percentage of the distance Li Fang runs is Wang Hong" to "What percentage of the distance Li Fang runs is Wang Hong"?
2. Try to answer and find the question:
Dialogue: Do you want to try to find out for yourself?
The students try to do it and say their names.
Dialogue: What problems did the students meet that need to be discussed?
3. Students communicate freely, and teachers guide their thinking in a timely manner:
(1) Discuss how to formulate
Thinking: Why? what do you think?
Introduction: Which two quantities are being compared and which quantity is regarded as the unit "1"? What percentage of the distance Li Fang runs is that of Wang Hong?
Summary: This question takes the distance run by Wang Hong as the unit "1", and the distance run by Li Fang is a few percent of that of Wang Hong. In fact, it's like asking Li Fang to run a few percent of Wang Hong to solve the problem.