I. Teaching content
1, a factor is the oral calculation of an integer.
2, two digits multiplied by two digits to write calculation and estimation.
3. Mixed operation.
Second, the teaching objectives
1, learn the oral arithmetic methods of integer ten times integer ten and integer ten times two digits, and be able to do oral arithmetic correctly; Learn to multiply two digits by two digits and calculate correctly; Two-digit multiplication estimation and simple mixed operation of multiplication and division can be carried out in combination with specific conditions.
2. Experience the process of exploring the calculation method of double-digit multiplication, and cultivate the consciousness of independent thinking and exploring problems; Experience the diversity of problem-solving strategies.
3. In the process of exploring the algorithm, I feel the application of multiplication in life and have a successful experience.
Third, material interpretation
1, material selection. Taking the beautiful street scene as the theme, it embodies the prosperity of the city and the beauty of the hometown.
2. Context string. This unit has four information windows, namely: beautiful street lamps-beautiful flower beds in the center of the street-magnificent sightseeing towers-colorful street night scenes.
Fourth, knowledge analysis.
1, knowledge base. There are three kinds: one is table multiplication; The second is the addition and oral calculation of numbers within 100; The third is two or three digits multiplied by one digit.
2. The status of teaching materials.
(1) Multiplying two digits by two digits is a complete multiplication (multiplying one digit by one digit is an in-table multiplication, and multiplying two or three digits by one digit is an incomplete multiplication). This is the most important part in multiplication teaching.
(2) It is the basis for learning to multiply three digits by two digits in the future;
(3) It is the basis for studying elementary arithmetic and solving problems in the future;
(4) It is the basis of learning fractional multiplication in the future.
3. Knowledge composition. This is a relatively large unit, * * * has four information windows, and the learning content of each information window is as follows:
Information window 1: integer ten multiplied by integer ten, integer ten multiplied by two digits for oral calculation, and decimal digits multiplied by two digits for written calculation.
Information window 2: simple calculation of carrying two digits multiplied by two digits, estimation of multiplying two digits by two digits, simple mixed operation of multiplication and division.
Information window 3: Complex carry two-digit multiplication is calculated with two-digit pen, and mixed operation of multiplication and division.
Information window 4: Comprehensive use of the knowledge of two-digit multiplication and multiplication and division to solve simple practical problems.
Interpretation of verb (Verb's abbreviation) Textbook
1, information window 1- beautiful street view
(1) This scene shows two students visiting the municipal government building: the towering municipal government building, the beautiful street lamps and the balloons celebrating provide rich information. Because the buildings are magnificent and tall, the streets are long and there are many balloons, these information can't be displayed intuitively. The data is displayed in the form of dialogues and tables.
(2) The setting and function of examples. This information window is designed with three red dots. 2 green dots ***5 examples.
The first red dot: How many balloons are there in the balloon group on the right? Formula 40×20 Learn the oral calculation of integer ten times integer ten.
Second red dot: How many balloons are there in the left balloon group? Formula 22×30 Learn the oral calculation of integer ten multiplied by two digits (no carry)
The third red dot: How many lights are there in this street? Formula 23 × 12 Learn the written calculation of multiplying two digits by two digits without carrying, which is the focus of this information window and this unit.
The first green dot: How many offices are there in the municipal office building? The formula 32×2 1 consolidates the previous knowledge.
The second green dot: How many offices are there in the news building? Formula 24×20 Learn a simple and convenient way to write a zero at the end of a factor with a pen.
(3) Problems that should be paid attention to in teaching.
(1) In teaching, teachers can start with students' existing life experience and let students talk about where they have been and where they have played. What do you see? Then show the scene in front of the city hall and guide the students to carefully observe where this picture is. What's in the picture? What math problems can you ask according to the information in the picture? Students can also talk about their hometown. Teachers can add some math information, and then students can ask questions.
(2) Strengthen oral calculation and estimation. In this information window, oral calculation, estimation and written calculation appear as strategies to solve problems. When solving the first and second red dot problems, although there are many strategies at the same time, the focus is on verbal calculation; When solving the third red dot problem, students may estimate it, may calculate it orally, or may calculate it in writing. Here, it is mainly written calculation.
③ Although solving the third red dot problem is a pen calculation, all parts of the product are not carried forward. We emphasize the basic method of learning to multiply two digits, highlight the writing position of the second part of the product, and understand the reason why the 0 in the second part of the product is not written. This question is the focus of this information window.
(4) When solving the second green dot, the teacher can ask the students to write the vertical form first. Generally speaking, students can't think of a simple way to write it. Teachers can prompt and guide them, and then understand why it is easier to write like this by comparison.
⑤ Independent exercises: * * Nine exercises were arranged.
Question 7, fill in the form, and present the order form for the third grade uniform of Ocean Primary School. In practice, students can talk about the meaning of unit price, quantity and total price in combination with their own life experience, and then calculate the figures to fill in the form. Pay attention to the total column and understand which columns should be filled in and which columns should not be filled in.
In question 9, in addition to completing the question (1), in question (2), students may ask, "How many trees are there in a * * *?" You can also add conditions and ask more questions.
2, information window 2-beautiful street flower beds
(1) This situation map shows the scene of urban street flower beds. Scenery such as flower beds, fountains and lamp posts provide rich mathematical information. This information is presented in the form of a dialogue between the installer and the information board label.
(2) The setting and function of examples. This information window is designed with three red dots representing three examples.
The first red dot: "Protect the environment" flower bed How many potted flowers did I use? Formula 27×23 Learn the calculation method of multiplying two digits by two digits (carry).
The second red dot: "Beautify Home" How many potted flowers did I use in my flower bed? Equation 22×28 Learn the estimation of two-digit times two-digit number.
The third red dot: There are still 30 such lampposts left. Are these bulbs enough? Solving problems by using mixed operation of multiplication and division.
(3) Problems that should be paid attention to in teaching.
(1) In teaching, teachers can take the scene of information window 1 to guide students to observe the situation diagram, sort out the mathematical information contained in the diagram, and put forward the multiplication problem. Students can also talk about the parks in their hometown and teachers can supplement relevant mathematical information according to local conditions, so that students can solve mathematical problems by multiplication.
According to past experience, the first red dot in this information window should be "There are 30 such lamp posts left. Are these bulbs enough?" This is the third red dot. If this question is hidden, students may ask the following questions: How many potted flowers are used to "protect the environment"? How many potted plants were used to beautify the flower bed? How many nozzles are there in a box? How many light bulbs did a * * * buy? These four questions can all be used as the first red dot. When dealing with the first red dot, let the students estimate the approximate range of the judgment result, and then let the students calculate vertically and report and exchange their own algorithms. The emphasis here is on simple carry. The first red dot is the focus of the information window.
(3) The second red dot focuses on estimation, which allows students to solve the problem freely in their favorite way, and then organizes students to communicate and talk about how they estimate (this is the focus of this red dot), that is, to highlight the estimation strategy.
(4) The third red dot clearly needs to solve the problem that "there are still 30 such lamp posts not installed. Are these bulbs enough?" This problem can be compared with the number of light bulbs needed to install 30 lampposts. You can also calculate how many light bulbs you can buy and how many lampposts you can install, and compare 30 lampposts. Then let the students calculate independently and solve the problem. It should be noted that the way to solve this problem is to let students experience different strategies to solve the problem through communication; Second, students can calculate step by step or comprehensively (this kind of questions advocates step-by-step solution); Third, don't put forward the type of "generalization problem", but pay attention to guiding students to carry out personalized learning.
⑤ Independent exercise: * * 8 questions were assigned.
Questions 5 and 7 are practical problems solved by multiplication. In practice, students can make up a story with mathematical information by looking at pictures, and then ask related mathematical questions and analyze and answer them independently. When organizing the communication again, let the students talk about their own ideas, why and how to present them like this.
6. Question 8 presents the scene of the school sports meeting, presenting a lot of data in the form of statistical tables, which is a set of practical problems solved by mixed operations of multiplication and division. In practice, let the students talk about the admission mode of the school sports meeting first, then show the pictures, guide the students to analyze the pictures and make clear the strategies to solve the problems. The key to this problem is to let students talk about their own problem-solving ideas.
⑦ Smart house is a matter of layout. Teachers should guide students to list all the situations in a certain order and cultivate students' orderly thinking. There are eight cases of this problem: plane-car-plane; Plane-car-train; Plane-train-plane; Plane-train-train; Ship-car-plane; Ship-car-train; Ship-train-plane; Ship-train-train.
3. Information Window 3- Grand Sightseeing Tower
(1) This scene shows students visiting the sightseeing tower. It provides a wealth of mathematical information such as the number of people boarding the sightseeing tower, the number of tickets and the vehicles passing through the intersection. The information was said by the staff, the students who were sightseeing and the traffic police.
(2) The setting and function of examples. This information window is designed with two red dots, which are two examples.
The first red dot: How many people go to the tower for sightseeing at most today? Formula 28×39 Learn the complex pen calculation of multiplying two digits by two digits (carry).
The second red dot: 100 yuan is enough for six tickets? Compare the formulas 30÷2×6 or 30×(6÷2) with 100, and learn to solve practical problems with simple mixed operation of multiplication and division.
(3) Problems that should be paid attention to in teaching.
① The topic of visiting the sightseeing tower can be introduced in teaching, and then students can be guided to observe the situation map carefully and find relevant mathematical problems according to the information in the map.
② The multiplication calculation of the first red dot problem is a complicated carry multiplication. In teaching, teachers can let students answer independently with their favorite methods, and then report their thoughts and practices, thus deepening their understanding of arithmetic and algorithms. The second method, if students can't figure it out, teachers should guide them, mainly to lay the foundation for students' estimation strategies.
(3) The second question marked with a red dot should be clearly solved: "Is 100 yuan enough to buy six tickets?" This question can be answered by "How much is a ticket?" You can also find out how many of these six tickets are two first. Let students realize the diversity of problem-solving strategies in communication. When solving problems, students can make step-by-step formulas or comprehensive formulas. It should be noted that teachers should not put forward the type of "standardization problem".
④ If students ask, "/kloc-how many vehicles pass through the intersection in 0/5 minutes?" And so on, you can let the study be done independently and do it as an exercise.
⑤ Independent exercise: * * Assigned 12 questions.
Question 7 is about the processing of sweaters in the knitting workshop. Quantitative relationship among infiltration efficiency, time and total work. Fill in the form first, then solve the problem. Students can also ask other questions.
The ninth question is the quantity and money of the dishes sold in the noodle restaurant. This topic contains a lot of information and questions. Students should carefully observe the pictures, sort out all kinds of information provided by the pictures, make clear the problems to be solved, and then make calculations. The second and third questions can be solved by the answer to the first question. If students don't use the answer to the first question, they should be praised by the teacher.
The problem 12 is a problem of finding laws. In practice, students can be guided to observe the first two groups of problems, find the characteristics of factor and product in each group of two formulas, find the law, then solve the last two groups of problems with the law, and then let students verify whether the law is correct through calculation. After completing the exercise, students can also ask other questions according to the law.
4. Information Window 4-Colorful Street View at Night
(1) This situation map presents a colorful street night scene. Including advertising lights beside the street, colorful neon lights in the square, colored lights on the trees, tourist sightseeing bus in the parking lot and other information. This information is presented in the form of tourists, businessmen and labels.
(2) Description of the information window. This information window only has situations, no examples and no exploration. Intention is the comprehensive application of what you have learned before. The comprehensive application here is to let students put forward relevant mathematical problems according to the information and choose their favorite methods to solve them. The key here is to let the students talk about the ways to solve the problem.
(3) Problems that should be paid attention to in teaching.
Looking at pictures is the key to this lesson. When teaching, students should look at pictures and understand the mathematical information in the pictures. Guide students to ask quality math questions, that is, ask students to ask relevant questions according to what they have learned before, and avoid asking some too simple questions.
It has been put forward in the textbook: how many cars do you need to rent a B car? Decorate the remaining 25 trees with 400 meters of colored lights. Is that enough?
Students may also ask the following questions: How much is the advertising lamp rent? How many light bulbs are there in a box?
We should solve the problems raised by students in the order from easy to difficult. Consolidate and improve the content learned in this unit in communication. There are not only the expansion and promotion of problem-solving strategies and methods, but also the exchange and consolidation of calculation methods.
(4) Independent exercise: * * Assigned 17 questions.
Question 5: If you want to know how far the happy community is from the Children's Palace, you need to know how many meters Kobayashi walks every minute on average. If you want to know how many meters Xiao Lin walks per minute on average, you need the answer to the first question. The formula is: 648÷9× 1 1.
Question 8 is a scene of a large parking lot, and the charging standard of the parking lot is provided in the table. Let the students answer independently first, then organize exchanges and talk about the ideas to solve the problem. (2) There are two payment methods, which are calculated separately and then compared.
15 students may be listed as the following formula: 43× 5× 2; 43×6×2; Students are asked to explain why the formula is so formulaic. As long as it makes sense, the teacher must affirm it.
In the exercise of 17, let the students talk about the relationship between the floor where they live and the number of stairs, and then solve it. Children in rural areas may not have similar experiences. Teachers can give familiar examples or physical demonstrations to help students understand the relationship between the number of floors and the number of stairs.
Did I learn? It is a comprehensive situation map of grassland pasture. The vast sketch of the original pasture contains rich mathematical information. Students can make full use of this situation to monitor their knowledge. Besides answering the questions in the textbook, students can also ask: How many horses and sheep are there? If each sheep eats 15 kg of grass every day, how many kg of grass do these sheep eat every day? When practicing, ask the students to complete the problem of equal two-step calculation independently, and then communicate with each other in groups and classes and evaluate collectively. On this basis, guide students to summarize the performance and main gains of this unit through review and reflection.
(5) Three digits are appropriately increased, and four digits are appropriately increased.