This lesson is the first lesson in Unit 4, Grade Three. Teacher Qin told me how many small trees there are (whole ten, whole hundred, whole thousand multiplied by one digit). This is a calculation course. In the past, there were always the following misunderstandings in the classroom teaching of calculation class: (1) Too much emphasis was placed on the introduction of situations and the warm-up of calculation thinking was ignored; (2) overemphasizing the diversity of methods and ignoring the optimal refinement of the algorithm; (3) Too much emphasis on problem solving, ignoring the necessary training. Teacher Qin's class provides us with a good solution strategy to avoid these misunderstandings.

Strategy 1: Pay attention to the arrangement of review preparation and promote the efficient transfer of knowledge.

The knowledge base for students to learn oral arithmetic of integer ten, integer hundred and integer thousand multiplied by one digit is the composition of multiplication and number in the table. So before class, the teacher set up two exercises to review, one is the listening and calculation exercise of multiplication in the table, and the other is the exercise about the composition of numbers. Through the training of these two questions, it lays a good foundation for students to successfully master the oral calculation methods and arithmetic of integer ten, integer hundred and integer thousand times one digit, and also promotes the positive transfer of knowledge.

Strategy 2: Pay attention to the optimization and integration of algorithms and strengthen the teaching of arithmetic algorithms.

In the process of exploring new knowledge, when teachers guide students to explore the algorithm of 3×20=, students present three methods: (1) the combination of several lines and the same number, (2) the way of enumerating one by one, and (3) the multiplication of an integer ten and a number is deduced by analogy, that is, 20 is regarded as two tens plus three. After the algorithm exchange, the teacher asked the students to observe these three methods carefully and think about their relationship. After independent thinking and group communication, students come to the conclusion that the first method and the second method are essentially the addition of three twenties. The first method is to understand with the help of several lines, and the second method is to understand with the help of physical objects (there are three bundles of trees in the theme map, and the number of bundles is 20). Both methods are to find three twenties. This leads students to communicate the relationship between addition and multiplication, that is, multiplication is a special form of addition. When comparing the differences between the first two methods and the third method, most students think that the third method is simpler than the first two methods, and a few students think that one of the first two methods is simpler. At this time, the teacher did not force the students to accept that the third method must be good, but asked: "If there are 9 bundles of saplings, how to calculate?" Only in this way can students really realize that the advantages of the third method are highlighted when the number increases a lot. Then ask the students to complete the textbook "How many trees are there in a bundle of four?"? How about five bundles? "After the students are independent, please ask them to talk about your ideas (reasoning) and how to calculate (induction). Let the students refine the algorithm: multiply the integer ten by one digit. When calculating, multiply this number by ten digits first, and then add a 0. In this way, students are guided to generate their own algorithms on the basis of rational calculation.

After students have mastered the arithmetic and algorithm of multiplying an integer by a number, when exploring the calculation method of multiplying an integer by a number 3×500=, most students can realize positive migration and directly say the arithmetic: 3×500 means how many are three 500 s, and three 500 s are 15, so it is1500; Algorithm: Multiply 5 on the hundredth by 3 to get 15, and then add 2 zeros directly after it.

Strategy 3: Pay attention to oral arithmetic training and consolidate the basic ability of calculation.

When reviewing this lesson, the teacher arranged the listening and calculating exercises of multiplication in the table, which laid a good foundation for the study of this lesson. After exploring and summarizing the calculation methods, the teacher showed a group of oral arithmetic exercises, so that students can master the calculation methods of oral multiplication of whole ten, whole hundred and whole thousand multiplied by one digit on the basis of certain training.

There is no overly gorgeous situation creation in this class, but the theme scene diagram in the textbook is selected to start teaching; There is no noisy group discussion, only the discussion that does not affect the volume control of other students at the same table after independent thinking; There is no exaggerated praise, only a pertinent evaluation after capturing students' thinking and good habits. Under the guidance of the teacher's organization, the classroom teaching of the whole class makes the teachers who participate in the class feel the changes quietly. Teacher Qin's simple and efficient math class provides a good example for our classroom teaching of computing class. ......