1. Understand the basic properties of decimals, and use the properties to simplify and rewrite decimals.

2. Explore and discover the essence of decimals by guessing, calculating, measuring, observing and comparing, and cultivate the good quality of exploring new knowledge.

3. Feel the process of seeing the essence through phenomena and the important role of mathematics in real life, and experience the fun of solving problems.

Emphasis and difficulty in teaching

Teaching emphasis: let students understand and master the nature of decimals.

Difficulties in teaching: being able to solve practical problems by applying the nature of decimals.

teaching tool

Ppt courseware

teaching process

Show the courseware and fill in the appropriate numbers in the brackets.

1 yuan = () Angle = () minutes 1 decimeter = () cm = () mm.

3 meters = () decimeter = () centimeter 5 yuan = () angle = () minute.

(A), create a situation to guide the inquiry

Teacher 1: The teacher learned that the price of a spoon in the shop is 3.00 yuan. How many are there in daily life? (3 yuan), what's the relationship between 3 yuan and 3.00 yuan? (3=3.00 yuan) The price tag for displaying a pair of gloves is 2.50 yuan. What is the usual 2.50 yuan? (2.5 yuan)

Teacher: Why is there a zero after 2.5 yuan? How many zeros can you add? We will learn this knowledge in this class.

Second, explore new knowledge and solve doubts in class

1. Teaching examples 1. Ask the students to measure three pieces of paper with the length of 0.1m0.0-1m0.001m.

What do you think are the lengths of these three pieces of paper?

(1) courseware shows the line segments of 1 decimeter,10cm,100mm.

Please compare their sizes. After a little thought, the students immediately asked questions and asked how you knew. (that is, the process of thinking)

Demonstration: Compare the dimensions of 1 decimeter,10cm and100mm by gravity method.

Write on the blackboard to demonstrate: 1 decimeter =10cm = 100 mm.

(2) Import example 1:

Can you rewrite them into decimals in meters?

According to the students' answers, it is concluded that 1 decimeter is110 meter, which is written as 0. 1 meter.

10 cm is101100m, written as 0. 10 m.

100 mm is10011000 m, written as 0.1000 m.

Book combination: 01m 0.1m 0.1m 0.

What is the relationship between the size of 0. 1 m, 0. 10 m, 0. 100 m?

Students answer the questions quickly and then demonstrate the courseware. And put an equal sign between them.

We can also compare them by weight. (Courseware demonstration)

(3) show the blackboard:

1 decimeter =10cm =100mm

0. 1 m = 0. 10 m = 0. 100 m 0.1= 0.10 = 0.

Q: What does this mean?

Please observe this equation carefully. You can look from left to right and then from right to left. what has changed? Where is this decimal (emphasis is on the end, not the back)? How do you say more (less) 0?

Introduction: Think about what 0.30 means? What about 0.3? How many squares should I draw?

After painting, the student asked, why do you paint like this? Then demonstrate the coloring process.

Q: Who painted a large area? What are the sizes of 0.30 and 0.3? how do you know

Visual comparison method: they all look the same size;

(Re-blackboard writing under the original blackboard: 0.30=0.3)

(5) As can be seen from the numerical sequence table, if zero is added or removed at the end of the decimal, and the digits of the remaining digits remain unchanged, then the size of the decimal remains unchanged.

Teacher: Can the zero in the middle of the decimal be removed? Can you add zero in the middle of the decimal point?

Student: No, because of this, the digits of the rest of the figures have changed, so the decimal places have also changed.

Teacher: Does that integer have this property? (Emphasize the difference between decimals and integers)

(6) Is the following statement correct?

(1 at the end of a number? 0? Or remove it? 0? The size of the decimal remains the same.

(2) Add? 0? Or remove it? 0? The size of the decimal remains the same.

(3) add? 0? Or remove it? 0? The size of the decimal remains the same.

(4) put the end of the decimal point? 0? If it is removed, its counting unit will change.

(v) Summary

Teacher: What is the essence of decimals?

Twelve. Job design

Complete the first question on page 64 of the textbook.

Write on the blackboard.

Properties of decimals

Observation: 1 decimeter =10cm = 100 mm.

0. 1m = 0. 10m = 0. 100m。

0. 1=0.0 1=0.00 1 0.3=0.30

Basic Properties of Decimals: Add or Divide at the End of Decimals? 0? The size of the decimal remains the same.

Comparison of the nature and size of decimals Teaching plan (2) Teaching objectives

Knowledge and skills

1. Guide students to understand and master the nature of decimals, and simplify and rewrite decimals by using the nature of decimals.

2. Cultivate students' practical ability to observe, compare, summarize and summarize.

3. Cultivate students' preliminary mathematical consciousness and thoughts, let students feel the internal connection of mathematical knowledge, and at the same time infiltrate the view that things can be transformed into each other under certain circumstances.

Process and method

Through the explanation and comparison of decimals, we can experience the learning methods of inquiry discovery and transfer reasoning.

Emotions, attitudes and values

Let students try to understand the nature of decimals, compare the size of decimals and understand the relationship between knowledge according to their existing life experience and mathematical knowledge, so as to cultivate students' awareness of autonomous learning and innovative spirit.

Emphasis and difficulty in teaching

Teaching emphasis: be able to read and write decimals correctly.

Teaching difficulty: mastering the numerical order of decimals.

teaching tool

Multimedia and blackboard writing

teaching process

Create situations and introduce new lessons.

Teacher: Students, are pencils and erasers the same price?

Student: Same, 0.3 yuan = 0.30 yuan.

Teacher: 0.3 is three zeros.1; 0.30 can also be regarded as three 0. 1. So the two are the same. Today, we will learn the properties of decimals and compare their sizes.

Title on the blackboard: Comparison of the nature and size of decimals

Fill in the blanks with pictures

0. 100m = 100mm； 0 0. 10/0m = 10/0cm; 0. 1 m = 1 decimeter

So 0.100m = 0.10m = 0.1m.

Teacher: From the above two groups of equations, we can draw the same point, that is, adding 0 or subtracting 0 at the end of the first number, and the resulting equation still holds.

Inductive summary: Add after decimal point? 0? Or remove it? 0? The size of decimals remains the same, which is the essence of decimals.

Learning and using:

Without changing the number size, change the following three decimal places to three decimal places.

0.4=0.400 3. 16=3. 160 10= 10.000

Second, explore new knowledge 2, decimal size comparison

Teacher: We have learned so many decimals, how can we determine their sizes?

Title of blackboard writing: comparison of decimal size

The teacher gave an example: color first and then compare the size. Compare 0.5 and 0.50.

Analysis: Divide 1 into 10 and take 5 copies, then these 5 copies can be written as 0.5, divide 1 into 100, take 50 copies, or write as 0.5, so the two are equal.

So 0.5=0.50.

(2) Compare 0.5 with 0.05.

Analysis: Divide 1 into 10, 0.5 is 5, 1 is 100, and 0.05 is 5, so 0.5 is greater than 0.05.

So 0.5 & gt0.05

(3)

Which is more expensive, the triangle ruler or the exercise book?

So: 0.6 & gt0.48.

We can get the same answer by drawing and comparing.

Analyze how to compare the size of two numbers;

0.6 and 0.48 compare the integer parts first, both of which are 0, so they are the same; Then compare the first place after the decimal point, 6 >; 4, so 0.6 is greater than 0.48, and so on. If the deciles are the same, compare the percentiles. . .

Summary: How to compare the sizes of decimals?

First, compare the sizes of the two decimal parts with the integer parts. If the integer parts are the same, the decimal parts are compared in turn from the tenth place.

Learning and using:

Compare the size of two numbers

6.4 and 5.8, 4.58 and 4.7, 0.54 and 0.576.

Answer: 6.4 > 5.8 4.58 < 4.7 0.54 < 0.576.

Summary after class

What did we learn in this class?

1, plus? 0? Or remove it? 0? The size of decimals remains the same, which is the essence of decimals.

2. According to the nature of decimals, they can usually be removed? 0? Simplify decimals

3. Compare the sizes of two decimal and integer parts first. If the integer parts are the same, compare the decimal parts in turn from the tenth place.

homework

1. Who scored high in junior competition?

Answer: 9.87

2. The scores of the three students are arranged in order. How should we arrange them?

Answer: Xiao Qiang scored 9.87, Xiao Gang scored 9.90 and Chen Ming scored 9.96, in the following order.

9.96 & gt9.90 >9.87

3. Find the positions of 8.5 and 9.2 in the above picture and compare the sizes.

8.5 & lt9.2

4. Arrange the following fish in order.

Answer: 5.01> 4.9 1 & gt； 4.2 & gt4.0 1 >3.79

2. Expand, promote and simplify decimals

Simplify the decimal on the left to the simplest form. (Delete 0)

2.80 yuan =2.8 yuan

4.00 Yuan =4 yuan

10.50 yuan = 10.5 yuan

Teacher's summary: As mentioned above, according to the nature of decimals, they can usually be removed? 0? Simplify decimals

And so on:

Judgment: The more digits after the decimal point, the larger the decimal point.

Answer:?

This statement is wrong. The decimal places can be equal, such as 0.300=0.3, or less than the decimal places, such as 0.03 less than 0.3.

Write on the blackboard.

Comparison of the nature and size of decimals

1, plus? 0? Or remove it? 0? The size of decimals remains the same, which is the essence of decimals.

2. According to the nature of decimals, they can usually be removed? 0? Simplify decimals

3. Compare the sizes of two decimal and integer parts first. If the integer parts are the same, compare the decimal parts in turn from the tenth place.