The teaching plan of "quotient divisor" in the first volume of mathematics in the fifth grade of People's Education Press.

Teaching objectives of 1

1 knowledge and skills:

Through concrete examples, we can understand the necessity of seeking quotient divisor, and think that seeking quotient divisor is the need of practical application.

2 process and method:

Master it? Rounding? The general method of intercepting approximate quotient by method.

3 Emotional attitudes and values:

When solving related practical problems, we can reasonably get the approximate number of quotient according to the actual situation, and cultivate students' interest in exploring mathematical problems and their ability to solve practical problems.

Emphasis and difficulty in teaching

1 teaching points:

Master it? Rounding? The general method of intercepting approximate quotient by method.

2 Teaching difficulties:

Understand the similarities and differences between quotient and product of divisor.

teaching tool

Ppt, title card

teaching process

Teaching process design

1 Review old knowledge and reveal topics.

1. Write the approximate decimal places in the table as required. (PPT courseware shows the topic. )

2. Find the approximate value of the product in the following questions. (PPT courseware shows the topic. )

The number of (1) has a decimal place: 2.83? 0.9;

(2) Keep two decimal places: 1.07? 0.56。

3. Reveal the theme: We have found the approximate value of the product in decimal multiplication. In fractional division, there are always infinite divisions, or quotient has many decimal places, but it is not needed in practical application and can be used as needed? Rounding? Methods Keep a certain number of decimal places and find the approximate number of quotients, which is what we will discuss in this lesson. (blackboard title: quotient divisor. )

2. Create situations and explore independently

1. Example 6 on page 32 of the textbook.

Dad bought a tube of badminton for Wang Peng. One tube is 12, and this tube is 19.4 yuan. How much is each one?

19.4? 12 ? 1.62 (yuan)

A: Each is about 1.62 yuan.

(1) The teacher instructs the students to calculate independently according to the information in the questions, and names the board. (Teachers patrol to understand the students' calculations and give appropriate guidance. )

(2) When students can't divide the quotient into two decimal places and three decimal places, teachers should promptly guide students to think: when calculating the price, it is usually only accurate to? Integral? What is the unit of measurement here? Yuan? How many decimal places should you keep? What should I do when I divide it? (Teachers should demonstrate on the blackboard or PPT courseware in time. )

① Students modify their own calculation flow after answering, and get 19.4? 12? 1.62 (yuan).

(2) After the revision, the teacher guides the students to make it clear that when the quotient retains two decimal places, it should be divided by the third decimal place and then divided by the third decimal place? Rounding? .

(3) Teachers further guide students to think: If you want to be accurate? Horn? How many decimal places should you keep? What should I do when I divide it?

① Students finish independently.

(2) After the revision, the teacher guides the students to make it clear that when the quotient keeps a decimal place, it should be divided by the second decimal place and then divided by the second decimal place. Rounding? . (Teachers should demonstrate on the blackboard or PPT courseware in time. )

(4) Teachers organize students to exchange and discuss.

(1) Through the above two calculations, how to find the approximate number of quotient?

② Teachers guide students to sum up: When seeking the divisor of quotient, calculate one more decimal place than the reserved decimal place, and then put the last one? Rounding? . (Teachers should demonstrate on the blackboard or PPT courseware in time. )

(5) Introduce a simple method to find the divisor of quotient: when finding the divisor of quotient, you don't need to continue division after reaching the number of decimal places to be reserved, just compare the remainder with the divisor.

(1) If the remainder is less than half of the divisor, it means that the next quotient is less than 5 and is discarded directly; (PPT courseware demonstration example 6 is accurate? Horn? The calculation process of. )

② If the remainder is equal to or greater than half of the divisor, it means that the next quotient is equal to or greater than 5, and the last digit of the quotient should be added with 1. (PPT courseware demonstration example 6 is accurate? Integral? The calculation process of. )

2. Compare the similarities and differences between the approximate values of quotient and quadrature.

(1) comparison? 1.07? 0.56? The divisor and solution of the product of? 19.4? 12? The approximate number of quotient, think about it, what are their similarities and differences in finding the law? (PPT courseware demonstration. )

(2) Thinking: What are the similarities and differences between quotient and quadrature? (PPT courseware demonstration. )

(3) Guide students to exchange and summarize. (PPT courseware demonstration. )

1 Similarity: Are they all pressed? Rounding? Method to obtain an approximation.

② Difference: When calculating the divisor of quotient, you only need to calculate one decimal place more than the decimal places to be reserved; When calculating the divisor of a product, it is necessary to calculate the whole product first, and then take the divisor.

3 Consolidate the application and internalize the method

1. Calculate the following problem.

Keep one decimal place: 4.8? 2.3? 2. 1

Keep two decimal places: 1.55? 3.9? 0.40

Reserved integer: 14.6? 3.4? four

(1) Students study independently, teachers patrol and give timely guidance.

(2) collective correction, the key point is to let students know how many decimal places each small question is divided into, and then how to get the approximate figures.

2. choose.

( 1)37.3? 2.7 The quotient with two decimal places is about (c).

a、 13.82 B、 13.80 C、 13.8 1

(2)23.5? The quotient (b) of 0.9 1 is 23.5.

A, less than b, greater than c, equals

3. Complete Exercise 8, Question 3 on page 36 of the textbook.

(1) Students practice independently, teachers patrol and give timely guidance.

(2) Organize students to communicate and compare various approximate methods to see which one is quick and simple. It is clear that only one column is listed from the overall situation, and if three decimal places are reserved at most, it is directly divided into the fourth decimal place, and then one decimal place, two decimal places and three decimal places are reserved, which is simple and not easy to make mistakes.

4. Judge right or wrong. (Yes, in brackets? , the typo in brackets? . )

(1) When calculating the divisor of quotient, it is calculated to be one more decimal place than the reserved decimal place, and then the last decimal place is? Rounding? . ( ? )

(2) When calculating the quotient, if it is accurate to the hundredth place, it must be divided into ten thousand places. ( ? )

(3) The divisor of quotient is the same as the divisor of product, and the exact number must be found first. ( ? )

A paving team is paving a section of road. Work for 3.5 hours in the morning, paving164.9 m; After working for 4.5 hours in the afternoon, I paved 206.7 m. Is it fast in the morning or in the afternoon?

(1) Guide the students to understand the meaning of the question and let them say, do you want to know? Is paving faster in the morning or in the afternoon? , what should I do? (Calculate the paving speed in the morning and afternoon respectively and compare the sizes. )

(2) Students calculate independently, and teachers patrol to find out that students keep different decimal places.

(3) Organize students to exchange information with different decimal places, and realize that as long as the speed is comparable, the fewer decimal places are simpler, and the accuracy can be determined according to the actual situation when the approximate value is clearly taken, and the decimal places can be flexibly selected.

Paving speed in the morning: 164.9? 3.5? 47. 1 (m)

Paving speed in the afternoon: 206.7? 4.5? 45.9 meters

47. 1 >45.9

A: Paving the road quickly in the morning.

6. Complete Exercise 8, Question 4 on page 36 of the textbook.

(1) How many times faster does a spider crawl than a snail?

(2) Can you ask other math questions and answer them?

(1) Guide students to examine the questions, so that students can understand that when there is no explicit requirement to keep decimal places in the questions, two decimal places should generally be kept.

(2) Guide students to make simple calculations consciously and flexibly. 1.9? 0.045? Become? 3.8? 0.09? ) and complete the question (1).

③ Complete question (2): Ask other math questions and answer them.

Summary after class

What did we learn in this class? What did you get?

Use rounding method to find the approximate value of quotient, which is generally divided to the next reserved bit; You can also look at the relationship between the remainder and the divisor after the divisor reaches the reserved digits (when the remainder is greater than or equal to half of the divisor, you can directly advance by one to get the approximate value of the quotient; If the remainder is less than half of the divisor, it is retained directly. ) Take the approximate value of the quotient.

Write on the blackboard.

Approximate quotient

Dad bought Xiaoming a bucket of badminton, one *** 12, and spent 19.4 yuan. How much is each?

19.4? 12 =1.61666666667 (yuan)

1. See how many decimal places or integers you need to keep. Keep two decimal places: 1.62.

2. Divide by the next number to keep. Keep one decimal place: 1.6.

3. visit? Rounding? Method to obtain an approximation of the quotient.

19.4? 12? 1.6 (yuan)

A: About1.One in 6 yuan?

Teaching plan of approximate number and business (2) teaching objectives

1, let students learn to use it? Rounding? Method to obtain an approximation of the quotient.

2. Cultivate students' practical ability and thinking flexibility, and cultivate students' ability to solve practical problems.

3. Guide students to think from different angles according to the actual situation in life and flexibly get the quotient.

Emphasis and difficulty in teaching

Teaching focus

Do you know why you want to make a quotient? Rounding? Method to obtain an approximation of the quotient.

Teaching difficulties

Can think from many angles according to the actual situation in life, and get the approximate number of quotient flexibly.

teaching tool

multimedia courseware

teaching process

First, review.

1, press? Rounding method? , the following figures keep one decimal place.

6.03、7.98

2. News? Rounding? Method, keep the following numbers to two decimal places.

8.785、7.602、4.003、2.897、3.996

3. Calculate 0.38? 1. 14。 (Figures shall be kept to two decimal places)

Second, the new lesson

1, teaching example 6:

The teacher gave example 6, dictation and recalculation. Students can't divide the quotient by two decimal places. The teacher asked: when actually calculating the amount of money, it is usually only cents. How many decimal places should we keep? Which one should I divide? Why? If you want to keep two decimal places, just work out three decimal places and press? Rounding method? The mantissa after omitting the percentile. )

The teacher asked: Is it final? Horn? How many decimal places do you need to keep? Which one should I divide? How much should it be equal to?

Teachers should make students think: How to find the approximate value of quotient (first of all, it depends on the requirements of the topic, and several decimal places should be reserved; Secondly, the quotient should be divided by one decimal place more than it needs to be kept, and then what? Rounding? . )

We have learned the approximation of quadrature and the approximation of quotient. What are the similarities and differences between them?

2.P32 Do it:

The teacher asked the students to calculate as required. Pay attention to whether the approximate value of quotient is correct when students calculate during the tour. After the lecture, let the students talk about how to get the approximate values of different quotients according to different requirements. (Calculate the number of decimal places of quotient to one more than the required number of decimal places, and then press? Rounding method? Omit the mantissa. )

Third, consolidate the practice.

1, find the approximate number of the following questions:

3.8 1? 7、32? 42、246.4? 13

2.P36 question 1.

Fourth, homework

P36 Question 4.

Summary after class

Class summary

Teacher: Students, what have you gained from this class?

homework

1, and calculate the following problem (the quotient is reserved for one decimal place).

14.36? 2.7 8.33? 6.2 7? 0.03 3)