1, material selection. Take "camping" activities that children are interested in as unit materials to stimulate children's desire to learn. For children who have participated in camping activities, they can recall the scenes of participating in camping activities at that time, relive the feelings of activities at that time, and find back the feelings that may have disappeared; For children who have never participated in camping activities, it can stimulate their desire to participate in such activities and cultivate students' love for nature.
2. The scene string of this unit. The device has two information windows. Conversely:
Divide food-set up a tent
Second, the unit knowledge analysis
1, knowledge base. There are two important foundations:
First, the preliminary understanding of division: the average score, the names of each part of the division formula (dividend, divisor, divisor, quotient), the division with dividend of 0 (if 0 is divided by any number that is not 0, it will get 0), the remainder and a scenario.
The second is division in the table: vertical division (divisibility), 2-5 division, 6-9 division and multiplication.
2. The status of teaching materials. There are four points:
Systematically understand the initial stage of division with remainder;
Help students form a preliminary and relatively complete cognitive system of division (both separable and inseparable);
It is the basis for learning to divide two or three digits by one digit in the future;
Is the basis to solve the problem.
3. Knowledge composition. * * * There are two information windows, and the learning content of each information window is as follows:
Information window 1: the meaning of remainder division, the writing and reading of formulas, and the relationship between remainder and divisor.
Information window 2: vertical writing of division.
Third, the interpretation of unit teaching materials
(1) Interpretation of information window 1
1, the interpretation of the scene diagram. The picture shows the scene of distributing food during camping activities. There are all kinds of food on the ground. The children are distributing all kinds of food easily. Four children are chasing and playing, and two children are talking about the feeling of activities. Judging from the activities and expressions of the characters, it conforms to the relaxed and natural characteristics of camping activities. Mountains, trees, birds and houses in the distance set off the scenery, showing a beautiful picture of "harmony between man and nature"
2. Information in the scene.
Useless information includes: the number of people playing backstage, trees, birds and other information.
Useful information includes: the number of people distributing food and the quantity of various foods.
Bread 9-4 people; 10 bowl of instant noodles-4 people;
Mineral water 1 1 bottle -4 people; 12 ham sausage-4 people;
Banana 13-4 people; Pear 14-4 people;
Apple 15-4 people; Chocolate 18-4 people.
3. The setting and function of examples. The information window is designed with 2 red dots, 1 green dots and 3 * * *.
The first red dot: 9 loaves of bread are distributed to 4 people on average. How to divide it? Learn the representation (writing) and reading method of division with remainder.
Green dot: How to divide other foods equally? Consolidate and strengthen the representation (writing) and reading method of division formula with remainder.
The second red dot: 18 How many people can the chocolate bar be divided equally? Learn the relationship between remainder and divisor.
4. Teaching strategies and matters needing attention
(1) Improving students' feelings about nature is the starting point of teaching. What aspects do students feel about nature? Through the activities, movements, expressions and moods of children participating in outdoor camping, these are the explicit expressions of children's happy mood; Reflected in the children's description of beautiful nature. Through the description of the above two aspects, we can promote the emotion of "harmony between man and nature"
(2) Understanding the meaning of average score is not only the basis for students to solve problems, but also an important basis for guiding students to abstract the essence of problems (abstracting "how to divide" with formulas is also the process and result of students' operation). Each copy has the same amount, which is called the average score-the average score can be expressed by □□ =□, which is an important basis for students in Grade Two.
(3) Learning the calculation of division formula with remainder is one of the goals of this lesson. In the next information window, students will use this foundation to learn the vertical writing of division with remainder, and at the same time consolidate and be proficient in the calculation of division with remainder.
(4) Difficulties for students to calculate the division formula with remainder: From the original knowledge system, students have learned to calculate the division formula that can be divisible by multiplication formula, and this lesson will learn the calculation of the division formula that cannot be divisible. From the form of surface formula, there is one more "remainder" than the original calculation, as if this is the difficulty of learning, but it is actually just an explicit expression of difficulty. The real difficulty is how students use the multiplication formula to think about which number in the division formula is closest to the dividend, such as 18÷4. When students think, they usually think from the formula of 4, that is, 14 gets 4...446, and only the formula of "446" can meet the needs of the final calculation, because only 16 is the closest. It is difficult for students to think that the dividend in the division formula is closest to the product in the multiplication formula.
5. Detailed explanation of example teaching.
Red dot one: conjecture-verification-reflection-sublimation.
Guess-not only lead students to guess "How should 9 loaves of bread be distributed to 4 people equally?" "How to divide" can be the result of final division or the process of division.
Verification-students use learning tools to explore and verify the process and results of "9 loaves of bread are distributed to 4 people equally"
Reflection and sublimation-first, guide students to express the process and results of points with mathematical diagrams, namely:
Then guide the students to express the result of the score with a formula, that is, 9÷4=2 (pieces) ... 1 (pieces).
The above learning process is actually a cognitive process of "operation-representation-calculation" from shallow to deep, from perceptual to rational.
Green dot: How to divide other foods equally?
Because there are many problems, it is suggested that teaching should be carried out at different levels, that is, teaching should be carried out at three levels, and each level should solve two or three problems respectively.
The teaching process at each level is carried out in accordance with "group inquiry-report exchange-summary".
Group Questioning-What is the answer to each question?
Reporting and communication-guide students to tell the inquiry process and inquiry results of each question.
Abstract generalization-guide students to abstract generalization with division formula.
Allow and remind students to use learning tools in the process of inquiry.
Red dot 2: 18 How many people can a chocolate bar be distributed equally?
In the above teaching, we have discussed the problem of "how much is given to four people on average and how much is left". As a complete knowledge system, we must also study the situation of "how much is given to everyone and how much is left", which is commonly called "inclusion and division". Red dot two is to study this problem.
Careful analysis of this problem, we can easily find that students are most likely to think of the multiplication formula (298,368) from the original knowledge system, so as to find the answer to the question. Teachers should guide students to abstract with mathematical formulas and let students express the meaning of each formula in mathematical language, and do both.
18÷9 (block) =2 (person)-each person is divided into 9 blocks, which can be distributed to 2 people.
18÷2 (block) =9 (person)-each person is divided into 2 pieces, which can be distributed to 9 people.
18÷6 (block) =3 (person)-each person is divided into 6 blocks, which can be distributed to 3 people.
18÷3 (block) =6 (person)-each person is divided into 3 pieces, which can be distributed to 6 people.
The above teaching is the first level, and the second level below uses the remainder to study the situation. Guide the students to divide each person into four, five, seven and eight blocks, and express how many people can be divided and how many blocks are left, and express them in mathematical language.
18÷4 (block) =4 (person) ... 2 (block)-each person is divided into 4 pieces, which can be distributed to 4 people, leaving 2 pieces.
18÷5 (block) =3 (person) ... 3 (block)-each person is divided into 5 pieces, which can be distributed to 3 people, leaving 3 pieces.
18÷7 (block) =2 (person) ... 4 (block)-each person is divided into 7 pieces, which can be distributed to 2 people, leaving 4 pieces.
18÷8 (block) =2 (person) ... 2 (block)-each person is divided into 8 pieces, which can be distributed to 2 people, leaving 2 pieces.
Finally, guide students to observe vertically and horizontally, and find the hidden law: the remainder is less than the divisor.
(b) Explanation of information window 2
1, the interpretation of the scene diagram. Many meaningful activities can be carried out in camping, such as the scene shown in the picture, where children are collecting wild fruits and mushrooms, grilled fish and setting up tents. These are all meaningful activities in camping. I believe that after seeing such pictures, children will have the idea of "I want to try it myself".
2. Information in the scene. There is a lot of information in the picture, including obvious information that can be asked and information that needs to be combined before asking questions. The information in the chart can be divided into four categories:
Fish sharing: 22-4 fish per person;
Divide wild fruits: 48-9 people on average;
Mushrooms: 55- 8 people on average;
Tent: 17 people-3 people live in each tent.
3. The setting and function of examples. The information window is designed with 2 red dots, 1 green dots and 3 * * *.
The first red dot: 4 fish for each person. How many people can 22 fish be divided into? Learn how to write vertical division with remainder.
Green dot: 48 wild fruits are distributed to 9 students on average. How much is each? Consolidate and strengthen the vertical writing of division with remainder.
The second red dot: How many tents do you need to set up? Using the knowledge of division with remainder to solve simple practical problems.
4. Teaching strategies and matters needing attention
(1) On the premise of sorting out the scene information, help students ask math questions. Classification is a good way to help students sort out what children are doing, and it is also a good way to help students sort out mathematical information.
(2) Learning how to use the remainder to calculate the division formula and understand arithmetic is one of the goals of this lesson. Compared with the previous information window, it is a reasonable understanding that in addition to improving skills, there are also requirements for cultivating the goal of mathematical thinking.
(3) Difficulties for students to calculate the division formula with remainder: The difficulty in the last information window is how to use the multiplication formula to think about which number in the division formula is closest to the dividend, that is, the thinking that the dividend in the division formula is closest to the "product" in the multiplication formula is the difficulty for students to calculate. The difficulty in learning this information window is to help students understand why the remainder is less than the dividend, that is, 22 ÷ 4 = () □, 4× () < 22, () should be the largest number.
5. Detailed explanation of example teaching.
Red dot one: each person gets four fish. How many people can 22 fish be divided into?
Solving problems-abstract sublimation
Problem solving-let students cooperate to solve problems, in short, it is to explore the final answer or result of the problem.
Abstract sublimation-first of all, the process and result of the above inquiry are expressed by formula (horizontal type); The second is to guide students to express the calculation process vertically; The third is the name of each part in the vertical division.
Green dot: 48 wild fruits are distributed to 9 students on average. How much is each?
After guiding the students to answer, use two formulas and two vertical forms to see the relationship between remainder and divisor. This is a further consolidation of the knowledge learning in the last information window.
As a consolidation of examples, it is necessary to show two more questions for students to answer, such as 33÷6 and 57÷9.
Use the above four topics to summarize:
22÷4=5......2 - 4×(5)