Examples and "Thinking and Doing" on pages 66-67 of Mathematics, an experimental textbook for the third grade of Compulsory Education Curriculum Standards published by Jiangsu Education Publishing House.

Teaching objectives:

1. Using life experience and existing fractional knowledge, through practical observation and hands-on operation, I initially understand the meaning of "finding the fraction of a number" and learn to answer the simple practical question of "finding the fraction of a number".

2. In the process of exploring and solving problems, further understand the practical significance of a part of the whole and develop the ability of abstract generalization.

3. Further understand the connection between the score and real life, and feel the significance and value of the score in solving practical problems.

Teaching process:

First of all, introduce.

There are four rabbits playing in the Woods. Mother rabbit brought their favorite carrots (the courseware highlights a plate of carrots with a cover in the theme scene, but you can see that it is carrots, but you can't see a few).

Ask a question: Give this dish of carrots to four rabbits equally. How much can each rabbit get from this dish of carrots?

Write on the blackboard after the students answer: This dish of carrots is 1/4.

Continuing description: Mother Rabbit also brought a dish and a dish of mushrooms (the courseware shows a dish and a dish of mushrooms).

Ask a question: divide this dish of vegetables and this dish of mushrooms equally among the four rabbits. How much can each rabbit get from this dish of vegetables? How many mushrooms do you have in this dish?

Students answer the blackboard: this dish is 1/4, and this dish of mushrooms is 1/4.

Follow-up: Why do rabbits share carrots, vegetables and mushrooms as 1/4?

Clear: regard a dish of carrots, vegetables and mushrooms as a whole and divide it into four parts on average, of which 1 part is a quarter of the whole.

【 Design Intention 】 Starting from dividing a dish of carrots, a dish of vegetables and a dish of mushrooms into four parts, each part is a score of the whole. Introducing the new curriculum will help to activate students' existing understanding of "a score of the whole", thus providing support for the next study. It covers carrots, vegetables and mushrooms, and regards the objects with outstanding average scores as a whole, which can effectively avoid the interference of the number of objects in the process of obtaining relevant scores.

Second, explore

1. Find what the whole 1/4 is.

Courseware demonstration: Bunny anxiously asked her mother that I got 1/4 for this dish of carrots. How many people are there? Mother rabbit uncovers the film covering carrots. The courseware hides 4 rabbits and highlights 8 carrots.

Ask a question: Do you know how many carrots 1/4 are? (blackboard writing: 8 carrots; What is 1/4? )

【 Design Intention 】 After the rabbit raised the question "What is the 1/4 of a plate of carrots", the courseware hid four rabbits and highlighted eight carrots. At the same time, the teacher put forward the question "How much is the 1/4 of eight carrots" in time, with the aim of guiding students' thinking to a new mathematical question "How much is the 1/4 of eight carrots", so as to avoid directly reducing the above practical problems to the integer division problem of "dividing eight carrots into four parts on average and finding out how much is each part", thus ensuring the smooth development of the new curriculum content.

Revelation: How many carrots are needed is 0/4 of 65438+8 carrots? Can you score a point with a stick first and find out the result?

(According to the students' operation, prompt appropriately: How many carrots are needed is 1/4, that is, divide the eight carrots into several parts and take a few. )

Make a request: can it be calculated continuously?

After the students answer, write: 8÷4=2 (root) on the blackboard, and add "Yes, 2" after "65438+ 0/4 of this carrot".

Ask: Why can I divide 8 by 4?

Further clarification: How many carrots does this dish need 1/4? That is, divide 8 carrots into 4 parts on average, and work out how much one part is, so divide 8 by 4.

Problem extension: one dish with four dishes and one dish with 12 mushrooms. How many 1/4 vegetables are there in this dish? What is the 1/4 of this dish of mushrooms? (Cooperate with the questioning courseware: a plate of four dishes and a plate of 12 mushrooms. At the same time, the blackboard asks, "What is the 1/4 of the four dishes?" And "What is the mushroom 1214?" )

Make a request: can you calculate directly?

Students try to calculate with a column chart.

Call the roll and answer according to the students' answers on the blackboard: 4÷4= 1 (tree), 12÷4=3 (tree). At the same time, add "1" after the original blackboard "this dish 1/4".

Introduction and comparison: What do the three questions mentioned above have in common?

Follow-up: What is the 1/4 of a plate of objects? It's all division calculation. Why do you get different results?

Key point: No matter how many carrots are 1/4, or how many vegetables are 1/4, and how many mushrooms are 1/4, these objects are divided into four parts on average, so the total number of objects is divided by four. Because the number of carrots, vegetables and mushrooms is different, their number 1/4 is naturally different.

【 Design Intention 】 From finding the number of a dish of carrots to finding the number of 1/4 of a dish of vegetables and 1/4 of a dish of mushrooms, although the number of the whole objects is different, the essence is to find a whole number of 1/4, divide the corresponding number of objects into four parts and take out 1/4. This kind of experience can not only help students gradually understand the mathematical meaning and corresponding mathematical methods of "how much is a number 1/4" in comparison, but also help students to deepen their understanding of the meaning of 1/4, which is used to express the relationship between parts and the whole, from a new perspective.

2. Find integers: 1/2, 1/8, 1/6.

Ask a question: If we ask how many 1/2 trees are in this dish, how should we count them continuously?

Students' independent formulaic calculation.

After the roll call, ask: What is the 1/2 of a dish? Why did you divide 2 by 4?

Question extension: If you ask how much carrots are 1/8 and how much mushrooms are 1/6, how should you calculate them continuously?

Students calculate separately.

In the communication report, students are required to focus on the thinking process in the statement.

Introduction and comparison: Why do you find that 1/4 of 8 carrots is divided by 4 and 1/8 of 8 carrots is divided by 8?

Follow-up: One dish has 12 mushrooms. 12 divided by 4, what's the score of this dish? How about 12 divided by 6?

Inspiration: What do you know from the above comparison?

Clarity: To find the score of a number is to divide the number into several parts equally, and to find a score can be calculated by division.

【 Design Intention 】 Through the comparison of the three groups, students can further realize that the same integer 1/4 and 1/2 are different, and so are the same integer 1/4 and 1/8.

Three. abstract

Guidance: through the study of this lesson, we know that a whole is divided into several parts on average, and one part is a fraction of the whole. What have we learned from today's study? What have you learned?

Fourth, practice

1. Guide to complete the "Want to Do" question 1. Let the students divide the picture first, and then fill in the formula.

Question: How many parts were the first bunch of strawberries divided equally? Why should it be divided into three equal parts? How many shares were divided equally in the second pile of strawberries? Why do you want to divide it evenly into four parts?

2. Guide to complete the second question "Thinking and Doing".

The teacher clearly asked the students to operate as required and calculate in parallel.

Problem: 1/2 of the wafer quantity is taken out twice. Why are the numbers different every time?

3. Guide to complete the third question "Thinking and Doing".

Ask the students to say the conditions and questions of the topic.

Make a request: guess, are the two people writing the same thing?

Follow-up: Who wrote more? Why?

After the students answer, they ask further questions: Is the calculation result the same as the judgment just now?

4. Guide to complete the fourth question "Think about it and do it".

Ask the students to say the conditions and questions of the topic.

Requirements: each fruit 1/3. Guess which fruit eats the most? What kind of fruit has the least quantity? Why?

Students calculate in the form of columns, and the whole class communicates.

5. Complete the fifth question of "Want to Do" independently.

6. Encourage students who have spare capacity to complete the thinking questions and organize corresponding discussions and exchanges.