I think Miss Li's teaching has the following highlights, which are worth learning:
1. Introduce situations, arouse students' enthusiasm and reveal topics.
Introduce the situation of boiling eggs in daily life. How many minutes does it take to boil one egg for 5 minutes and six eggs? Some students say 5*6=30 (minutes), others say 5 minutes, which naturally leads to the focus of today's teaching and the choice of the best scheme.
Second, pay attention to students' hands-on ability. When teaching pancake problems, Mr. Li asked students to take out circular pieces of paper prepared in advance to simulate the pancake process, so that students could experience the practicality and life style of mathematics in hands-on operation, and it could help them to choose the best scheme better.
Third, give full play to the team's ability of unity and cooperation, so that students can truly become the masters of the classroom. When exploring the best scheme of three pancakes, the teacher handed over the class to the students. Let the students begin to pose, then fill in the form, and finally report the results to the team leader. A series of activities, teachers let students go, teachers just do the necessary guidance, fully embodies the student-oriented thinking.
Four: Teachers are good at guiding and instructing students. Finally, the teacher organized the students to carefully observe the form and encouraged them to "What did you find?". Let students speak freely and spread their thinking. In the classroom, some students found the law that "the number of cakes increases 1 and the number of minutes increases by 3" at a glance, but no students came up with the method as mentioned in the teaching reference book. The teacher guides the instruction in time. If the number of cakes to be branded is even, two cakes can be branded. If the number of cakes to be branded is odd, two cakes can be branded first, and the last three cakes can be branded according to the above optimal method, which saves the most time. "
Suggestion:
1. When reporting the problem of flipping three cakes in the group, the teacher might as well put a little blackboard writing on the blackboard to facilitate students' understanding in the next step, because it is necessary to clarify the front and back sides of the three cakes.
2. When the group leader reports, the teacher should give the students a full opportunity to express their thoughts, so that after the students finish, the teacher can explain and guide them, and should not rush to interrupt the students' thinking.
3. When working in groups of four, I found that basically only two people participated in each group, and the other two did not participate. Teachers might as well do activities in groups of two, so as to give every student a chance to operate. After clearly flipping three cakes, the teacher asked the deskmate to talk about the best plan just now. I think it is a bit restrictive for students' thinking, so students should be allowed to think according to their own ideas.
4. In teaching, I think teachers should guide and instruct the best scheme in a certain order: "How many cakes should be baked-one * * * how many sides should be baked-at most two sides at a time, at least several times-and finally calculate the number of minutes needed", which is easier for students to accept step by step, and also conducive to students' final understanding of the law.
5. When the final rule is presented, I think that the rule of "number of cakes *3= number of minutes" is actually simpler, more intuitive and more in line with their understanding characteristics. Students will feel confused if they divide the number of cakes into singular and even numbers.
The problem of pancakes is the content of the first volume of compulsory education curriculum standard experimental textbook, which is published by People's Education Press. This paper mainly discusses how to arrange the operation reasonably to save the most time, so that students can experience the application of optimization thought in solving problems. Pancake is a common housework in our daily life, but it contains profound mathematical problems and ideas. The purpose of textbook arrangement is to let students try to find the best solution from a variety of solutions to problems through simple examples of pancake in daily life, so as to infiltrate students with the idea of optimization, let students experience the role of overall planning in daily life and make them feel the charm of mathematics.
First, go straight to the point, introduce new lessons, and reflect the beauty of simplicity.
In this class, the teacher started teaching with the clue of "everyone in the class bakes a cake", grasped the students' curious nature, and designed the life scene of "baking a cake" to directly expose the topic and introduce a new lesson. This not only makes students understand what they have learned in this class, but also quickly concentrates students' attention and stimulates their interest in learning mathematics. It is simple and clear, which embodies the beauty of simplicity in mathematics.
Second, pay attention to questioning, highlight details and reflect the beauty of details.
Teacher Fang pays special attention to the questioning of details in this class. He can listen carefully to students' words, ask questions when students are vague, ask questions when students don't understand, ask questions when breakthroughs are important and difficult, ask questions when the class is generated, pay attention to generation, and pay attention to guidance. From the questioning, we can see Mr. Yu's guiding art and the pursuit of detail beauty in mathematics.
Third, it breaks through the teaching difficulties of the textbook and permeates the idea of optimization.
At the beginning of the class, Mr. Fang made good use of the method of baking one cake and two cakes, and asked the students: Why is it the same time to bake one cake and two cakes? So that students initially established the concept of saving time by baking two cakes in one pot at the same time. Then, the method of baking three cakes is discussed with students. In this process, students are organized to discuss, report and demonstrate at the same table, and then students discuss, form a scheme of baking cakes, show students' schemes, compare and distinguish the differences between the two schemes, so as to optimize the scheme. The method of flipping three cakes is the key and difficult point here. Let the students discuss, cooperate and explore this problem, and then solve the problem, and then use the form to find the time for four, five, ... these cakes. The purpose of this treatment is to reduce the difficulty of the topic, to help students think and solve problems, and then to guide students to observe the table and discuss which is more convenient, the ordinary flipping method or the quick flipping method. "What did you find?" Let students choose the best scheme through observation and comparison, and finally sum up that the number of cakes × the time taken for a cake = the time required for the number of cakes. The whole process of baking cakes is progressive step by step, which cultivates students' mathematical thinking.
The fourth grade "Mathematical Wide-angle Pancake Problem" Review Draft 3 Pancake is a math class that permeates the overall optimization idea, and it permeates the simple optimization idea through simple optimization problems. In the process of teaching design and teaching, pancake is the theme, and the learning of mathematical thinking method is the main line. How can pancake be eaten as soon as possible? Start teaching. The inquiry process of flipping 1 sheet, 2 sheets, 3 sheets-single sheet and double sheet cakes was designed. Taking flipping three cakes as the breakthrough point in teaching, the consciousness of finding the best scheme from various schemes is formed, which provides students with time and space for independent thinking, hands-on operation, cooperative exploration and exhibition and communication. Students use small discs in their hands instead of cakes, and experience the process of putting forward and solving mathematical problems, discovering mathematical laws and constructing mathematical models. The whole class is permeated with the following ideas:
1, let the students practice.
Curriculum Standard for Number of Classes points out that students' mathematics learning content should be realistic, meaningful and challenging. In the class, the teacher asked the students to explicitly ask for a round piece of paper to replace the cake and make pancakes with their deskmates. This link allows students to participate in the process of knowledge generation, perceive in operation and sublimate in practice. Students are also required to use learning tools to simulate pancakes at the same table. One person cooks pancakes and one person records them.
2. Let students speak freely.
In class, the teacher asked the students to communicate, show and communicate with the whole class in groups. This link realized the equal dialogue between students and between teachers and students, which is not only the interaction between students but also the interaction between teachers and students. Through mutual communication, we can learn from each other's strengths and constantly improve our own cognitive system, forming an organized and regular knowledge structure. When studying how long it takes to bake three cakes (this is the focus and difficulty of this course), everyone has never used the method of baking one cake after another, but there are many methods to bake one after two cakes appear, and individual groups think of alternating baking. Teachers let students demonstrate and explain by hand, and everyone basically understands it. Later, everyone knows to make full use of the condition that they can bake two cakes at a time.
I think if this class can give children another development class, it can be arranged at the end of the class. What if there are 4 cakes, 5 cakes and n cakes to be baked? What did you find? The rule that the number of cakes is 3 = time is directly found, and the result is: if the number of cakes to be baked is even, two cakes can be baked; if the number of cakes to be baked is odd, two cakes can be baked first, and the last three cakes can be baked according to the above optimal method, which will save the most time. Students' findings are actually simpler and more intuitive. Mathematics teaching is not only the result of imparting knowledge, but more importantly, exploring the formation process of knowledge. It is not only a place to carry mathematical knowledge, but also a place for students to develop in an all-round way. Only by constantly strengthening learning and improving professional skills can teachers give students an innovative classroom and a developing classroom.