Teaching objectives

1. Let the students understand the meaning of percentage and read and write percentage correctly.

2. Guide students to understand that percentage is also a multiple relationship between two quantities, and at the same time understand the mutual relationship and development law of things, and cultivate students' ability of analysis and generalization.

Teaching emphases and difficulties

Understand the meaning of percentage.

teaching process

Review preparation

1. In daily life, students will often see or hear such numbers: (show projection)

(1) 12 Asian Games, the number of gold medals in various countries is as follows: China accounted for 40.3%, South Korea accounted for 18.5%, Japan accounted for 17.4%, and other countries accounted for 23.8%.

(2) In the final exam, 85% of the students in Class 5 (3) got excellent grades, and 15% reached the standard.

Q: Who knows what these numbers are?

Teacher: This is the percentage. In production, work and life, percentage is often used for investigation, statistics, analysis and comparison. What is a percentage? How to read and write percentages is what we learn in this class.

Words on the blackboard: the meaning and writing of percentage.

Before learning a new lesson, we should review relevant knowledge.

Question: Do the results of these two questions have the same meaning?

It's a fraction )

Introducing a new lesson: From the above two questions, we can see that the score can not only represent the quantity, but also represent the multiple relationship between the two quantities. Please look at the scores of the following questions. What do you mean by the percentage we study today?

(2) teaching new courses

(projection)

1. Grade 6 students in a primary school 100, Grade 3 students 17, and Grade 5 students 30. What percentage of the third-class students in the sixth grade account for the whole grade? What percentage of third-class students in the fifth grade account for the whole grade?

Question: How to answer the first question in a row?

Question: What percentage of students in the fifth grade are three good students? How come?

Question: According to the figures obtained, can you tell at a glance which grade has a high proportion of three good students? Can you compare their sizes directly? Why? It is not easy to see that the numerator is different and the denominator is different. )

Discussion: What can I do to compare two scores easily? (average score, the same score as mom. ) according to what? (The basic nature of the score. )

Teacher's summary: When comparing scores of different denominators like this, it is generally necessary to divide the scores to make the denominators the same. Especially in daily life, production and scientific research, the denominator is usually converted into a score of 100, which is convenient for comparison. Let's change these two numbers into fractions with the denominator of 100.

A few also show the multiple relationship between miyoshi students and the total number of students in the grade. )

2. practice. (display projection)

(1) A factory selected 500 pieces from a batch of products, and 490 pieces passed the inspection. What's the pass rate?

Multiple relationship between products and total products. )

There are 900 literature books and 450 story books in the school library. What percentage of literary books are story books?

3. Summarize the meaning of percentage.

What? (indicate the percentage of one number to another)

Question: Please think about it. What is a percentage? What is the relationship between the two quantities? (group discussion)

Summary: A number indicating that one number is a percentage of another number is called a percentage, and a percentage is also called a percentage or a percentage.

Question: What is the relationship between two numbers? (multiple relationships. ) Should there be a company name?

4. Learn how to read and write percentages.

Question: What are the similarities and differences between percentage and score ratio? (Similarity: Both indicate the multiple relationship between two quantities. Difference: Different forms. )

What form should the percentage be expressed in?

(1) Writing: When writing percentage, it is generally written as (%) instead of fraction. When writing percentages, remove the fractional lines and denominator, and add hundreds of semicolons after the numerator. For example:

(blackboard writing) 90% writing 90%;

64% writing 64%;

108.5% writing 108.5%.

(2) Reading method: When reading percentages, as long as the percentage sign is regarded as the denominator of 100 and the number before the percentage sign is regarded as the numerator, you can read like a fraction. For example:

17% ? Read seventeen percent;

0.03% is read as 0.03%;

15.2% is pronounced as 15.2%.

5. The connection and difference between percentage and score. (discussion)

Percentage is a kind of situation in a score. Fraction can indicate a specific quantity, or it can indicate that one number is a fraction of another number, so there may or may not be a unit of measurement behind the score; Percent only represents the multiple relationship between two quantities, so there is no unit of measurement.

(3) Consolidate exercises

1. 125 "do", do it in the book, and then modify it.

2. 126, 1 2 is written in the exercise book.

3. (Projection) Judgment:

(1) A fraction with a denominator of 100 is called a percentage.

( )

( )

(3) The denominator of the percentage must be 100.

( )

(4) There are 45 students in Class 5 (3), and all of them in physical education class have reached the standard, with a compliance rate of 100%.

( )

4. Fill in the blanks:

(1) read 40% of a book, indicating that () accounts for 40% of (). If the book is 100 page, read page (); This book has 200 pages, and I have read () pages.

(2) An expressway has been repaired by 25%, and the remaining ()% has not been completed.

(3) The speed of the train is 25% faster than that of the car, and the speed of the train is ()% of that of the car.

This is a very difficult question, because with the foundation of fractional application problems, students can discuss and answer.

5. The output value of a factory in 10 is equivalent to 108% in September. Write this percentage. Is the output value in October more or less than that in September?

(D) class summary

What did we learn in this class? The meaning, reading and writing of percentage. )

Do you know when people use percentages in their daily production and life? (in the calculation of excellent rate, qualified rate, sports compliance rate, etc. )

Teacher: Percentages are widely used, so I hope students can learn percentages well and learn to apply them in practice.

(5) Transfer

(omitted)