Xu Bo, No.20 Primary School, Jiamusi, Heilongjiang Province

Teaching purpose:

1, so that students can understand the meaning of percentage, read and write percentage correctly, and understand its application in real life.

2. Cultivate students' ability of abstraction, generalization, analysis and comparison by creating situations.

3. Stimulate students' interest in learning and make them feel that mathematics is inseparable from life.

Teaching focus:

1, let students understand the meaning of percentage.

2. Let students skillfully read and write percentages.

Teaching difficulty: let students understand the connection and difference between percentage and score.

Teaching preparation: multimedia courseware, the percentage information collected by students in life.

Teaching process:

First, create a scene and get the percentage.

Teacher: Students, what is the hottest topic in our sixth grade physical education class class now?

Health: Basketball match.

Teacher: Did our class compete? (compared. )

Teacher: Win or lose? (lost. )

Teacher: What a pity! What do you think is the key to winning this competition?

Health: accurate shooting.

Teacher: Look, how fierce the competition is. In the next competition, you must choose students who can shoot accurately. How to choose them reasonably? Teacher, here is a statistic. Can you explain who should play according to our previous mathematical knowledge?

Show me the form.

(full name)

Pitch number

Hit number

Gao Zhenda

25

14

Xu

20

1 1

Sonda

50

27

Student discussion

Student: Choose Xu Mu Xin because he missed the least;

Student: No, if a person throws the ball only once and misses it, can he be chosen, even though he has the least mistakes?

Teacher: No, is there any other way?

Student: According to the investment of 100, they invested 56, 55 and 54 respectively, so Gao Zhenda should be chosen.

Health: You can also check the shooting percentage. Then compare the sizes, and you can clearly see who is the most suitable to play.

Teacher: Yes, ask whose hit is more reasonable than Gao. (courseware)

Teacher: Like these fractions whose denominator is 100, we can also express them like this. Do you know these figures?

Health: Yes, percentage.

Teacher: Yes, that's what we are going to learn today.

Second, information exchange, understanding the meaning of percentage

Teacher: What do you want to know about percentages?

Health: I wonder what the percentage is?

Health: I don't know what percentage is used for life.

Health: Want to know the pronunciation and writing of percentage?

Student: I wonder what's the difference between percentage and score?

Student: I want to know how percentages, fractions and decimals interact. ┅┅

(blackboard writing: the difference between meaning and score, usage, writing and reading ┅ ┅)

Teacher: Let's learn this knowledge first in this class, and then continue to learn the rest in the next class.

Teacher: Before class, all the students collected the percentage data of their lives, right?

Health: Yes.

Teacher: Please choose your favorite sentence and share it with everyone (courseware).

Student: Students read different percentages and try to say what this percentage means. (omitted)

Teacher: The teacher also collected a message here:

There were 2740 students in the 20th primary school last year, accounting for about 14. 1% in the sixth school year. The qualified rate of graduates reached 100%, and the excellent rate of graduates reached 3 1.7%.

Teacher: Who wants to read it? (Ask a classmate to read it)

Teacher: What percentage?

Sheng Qi said: Three.

Teacher: Can you choose one of them and tell me what it means?

Students: The first item indicates that the number of sixth-grade graduates accounts for 14. 1% of the total number of students in the school.

Student: The second percentage means that qualified graduates account for 100% of the total number of graduates.

Student: The third percentage indicates that outstanding graduates account for 3 1.7% of the total number of graduates.

Teacher: (explain what these three percentages mean), what do you think these three percentages have in common?

Health: This is about finding out who is who.

Teacher: Can you use one number and another?

Health: All numbers represent the percentage that one number is another.

Teacher: Can you sum up a few percent?

Health: That is to say, find out the percentage of one number to another. (meaning of writing on the blackboard)

Teacher: Let's look at the pitching materials again. Now, can you choose one of these three percentages to explain its meaning?

Health: 56% means that Gao Zhenda's hits account for 56% of the pitches.

Health: 55% means that the number of hits made accounts for 55% of the pitches.

Health: 54% means that Song Da's hits account for 54% of the pitches.

Teacher: Like the percentage of these shots in the number of pitches, we can also call it hit rate. There are also the qualified rate and excellent rate we just mentioned, which can be expressed in percentage. There are many examples in life, attendance, germination rate, oil yield, survival rate ... these ratios are all expressed in percentage, so what else should you call percentage?

Health: It should also be called percentage.

Teacher: Your idea is very accurate. (Percentage of blackboard writing)

Teacher: Students, please look at the concept of percentage. Is it similar to what we learned before?

Health: comparative knowledge.

Teacher: What are the similarities?

Student: They all express the relationship between two numbers.

Teacher: Can percentage be regarded as a special form of ratio?

Health: I think so.

Teacher: What's so special about it?

Health: The clauses behind the percentage ratio are all 100.

Teacher: What percentage can you call it?

Health: It should also be called percentage.

Teacher: Yes. (Percentage of blackboard writing)

Teacher: OK, now please read the concept of percentage completely.

Third, cooperative inquiry, the difference between percentage and score

Teacher: We know what the percentage is. Can you tell me the difference between percentage and score according to your knowledge?

Student: The pronunciation is different.

Teacher: Can you give an example?

Student: The score can be read as 100% and the percentage can be read as 1%.

Teacher: Did you hear the difference?

Sheng Qi said: I heard it.

Health: The style of writing is also different. Write the fractional line first, then the denominator, and finally the numerator; And the percentage is to write the numerator first, then the percentage sign.

Teacher: (The blackboard with a percent sign), do you know this symbol?

Sheng Qi said: Yes, percentage sign.

Student: Molecules are different. Fractions can only be natural numbers, and percentages can be decimals.

Student: The denominator is different, too. The denominator of a fraction can be any non-zero natural number, and the denominator of a percentage can only be one hundred.

Student: Different denominators have different units. As long as the denominator is a few, the unit of a fraction is a fraction, and the unit of a percentage can only be one percent.

Student: The meaning is different. Fraction is to divide a number into several parts, which means one or several parts. Percent means to find out what percentage of one number is another.

Teacher: You mean something different. This is the most fundamental difference between percentage and score. Students, please.

Look at this question:

Now, please look at which of the following scores can be expressed as percentages? What can't?

1, a pile of 97/ 100 tons of coal, of which 75/ 100 was transported away.

2.23/ 100 meter is equivalent to 50/ 100 of 46/ 100 meter.

Health: Of these two sentences, 75/ 100 and 50/ 100 can be expressed as percentages, but the other three cannot.

Teacher: Why?

Student: Percentage can only represent the relationship between two numbers, not a specific number.

Teacher: Then can you sum up the difference in meaning between percentage and score?

Student: The significance of a score is that it can not only represent a specific quantity, but also represent the multiple relationship between two numbers. But the meaning of percentage can only express the multiple relationship between two numbers.

Fourth, the role of percentage in reading comprehension

Teacher: From the comparison just now, we know that percentage can only express the multiple relationship between two numbers, and fraction can not only express the specific quantity, but also express the multiple relationship between two numbers. Why does that percentage exist? What are the benefits of percentage in practical application? Students turn to page 104 to see if they can find a reasonable explanation. (Students read books)

Health: As far as I know, the biggest advantage of percentage is that it is convenient for statistics and comparison.

Teacher: OK, let's look at a set of data. What information can you get from comparing these percentages?

1, the population of China accounts for 2 1% of the world's total population, and the cultivated land in China accounts for 7% of the world's total cultivated land.

Disposable chopsticks were invented by Japanese. Japan's forest coverage rate is as high as 65%, but their disposable chopsticks are imported. The forest coverage rate of China is less than 14%, but it is a big exporter of disposable chopsticks.

3.2000 Sydney Olympic Games: China won 28 gold medals, accounting for 9% of the total gold medals; 2004 Athens Olympic Games: China won 32 gold medals, accounting for 65,438+00.6% of the total gold medals.

Health: From the first message, we can feel that China's population accounts for 2 1% of the world's population, which means that China has a large population, but China's cultivated land only accounts for 7% of the world's total cultivated land. From the comparison of these two percentages, I think our country should control the population.

Health: From these two percentages, we can know that China is great. It uses 7% of the land, but raises 265,438+0% of the world population.

Health: From the second message, I can feel that our country should pay attention to protecting forest resources and stop cutting down indiscriminately.

Health: From the third message, I can feel that sports in our country are constantly developing and progressing.

Teacher: As the saying goes, a glass of milk is stronger than a nation. Now milk has become an important food in our life. When choosing milk, you can also compare it by percentage and then make a choice.

Health: Of these two bright milk, I should choose the second one, because the second one has less fat.

Health: I'll take the first one. protein content is relatively high.

Teacher: Different people make different choices according to the content percentage. It seems that there is mathematics knowledge everywhere in life!

Students evaluate each other and sum up the percentage of writing.

Teacher: In the communication just now, I know that students can already read percentages. Can they write?

Sheng Qi said: Yes.

Teacher: OK, take out your notebook and write down the following percentages. Pay attention to the writing standard. Who wants to write in the front?

Let two students write on the blackboard, one with white chalk and the other with yellow chalk. Other students write quietly below. )

Teacher: Can you tell me how much you wrote? Can you tell me the percentage you have completed?

Health: I wrote six articles and finished 60%.

Health: I wrote seven articles and finished 70%.

Teacher: Can you let everyone guess how many you have finished?

Health: I finished 65%.

Health: He wrote six and a half.

Teacher: Can you put it another way to make it more difficult?

Health: I still have 10% unfinished.

Health: He wrote nine. ……

Teacher: Let's take a look at what the first two students wrote. Who do you think writes better?

Health: I think it's well written in white chalk. The two circles of the percent sign are symmetrical in size.

Health: I also think it's good to write with white chalk. The distance between the percent sign and the front molecule is moderate.

Health: I think the two circles of the percent sign must not be written too big, otherwise it will be easily confused with the zero of the molecule.

Teacher: According to the writing method just summarized, let's finish the above tasks.

Six, flexible application, solve practical problems

Teacher: OK, let's look back. What did you gain from this class?

(Students tell their harvest)

Teacher: Did you learn all these things just now?

Health: Yes.

Teacher: Has it reached 100%?

Health (loudly): Yes.

Teacher: OK, let's verify it.

1, fill in the blanks

Choose the appropriate number to fill in ()

45% 200% 98% 0.00 1% 75/ 100 100% 3.9%

(1) A book has read the whole book (), and there are 55% of the whole book left;

(2) A wire is () meters long;

(3) A car is seriously overloaded with limited load (). Drivers will have their driving licenses revoked;

(4) Do you think the possibility of finding a needle in a haystack is ()

2. Teacher: Finding a needle in a haystack is an idiom. 0.00 1% can be used to illustrate that the possibility is very small. Our Shenzhou series spacecraft in China have been successfully launched six times. Can you use an idiom to express it?

Health: 100% winning rate.

Teacher: Can it be expressed as a percentage?

Health: 100%.

Teacher: Can you also say an idiom expressed in percentage? Can you give me some specific figures?

Health: one in a hundred, 1%.

Health: As sure as a gun, 90%.

Health: Kill two birds with one stone, 200%.

……

3. Draw a picture and express 50% (omitted) in your favorite way.

4. Teacher: The only regret of the students in our twentieth primary school is that our playground is too small. They all hope that the playground can be expanded. This wish will come true. Look, this is a design of the future playground designed for us by a junior. Can you tell the proportion of various colored bricks with percentage knowledge?

Health: Yellow accounts for 24% of the total area.

Health: Green accounts for 24% of the total area.

Health: There are as many yellow ones as green ones.

Health: The gray ones account for 52% of the total area.

Health: Three kinds of bricks account for 100% of the total area.

Seven, class summary

Teacher: This class is almost over. The teacher is satisfied with the students' performance in this class. 100%. How satisfied are you with your performance?

Teacher: Only those who don't know enough can make progress. I believe that our students in Class Two, Grade Six, as long as 100% believe in themselves and 100% work hard, they will surely achieve 100% success. Ok, this class is over.

References:

The Significance and Writing Method of Percentages —— The Blog of Jiamusi Mathematics Base