New Century Edition Third Grade Mathematics Volume 2 How many trees are there in decimals? Lesson evaluation materials

This lesson is the first lesson of the fourth unit of the third grade taught by Teacher Qin, "How Many Small Trees Are There" (oral multiplication of whole tens, whole hundreds, and whole thousand by single digits). This is a computing class. The following misunderstandings often exist in previous computing class teaching: (1) Overemphasis on situational introduction and neglect of warm-up of computational thinking; (2) Overemphasis on diverse methods and neglect of algorithm optimization Refining; (3) Overemphasis on problem solving and ignoring the necessary amount of training. , Teacher Qin’s class provides us with a good solution strategy to avoid these misunderstandings.

Strategy 1: Pay attention to arranging review preparations to promote efficient transfer of knowledge.

The knowledge basis for students to learn oral multiplication of whole tens, whole hundreds, and whole thousand by single digits is the composition of multiplication sums in tables. Therefore, the teacher set up two major questions to prepare for the review before class. One is listening and arithmetic exercises for multiplication in tables, and the other is exercises related to the composition of numbers. Through the training of these two questions, it has laid a good foundation for students to successfully master the calculation methods and arithmetic of oral multiplication of whole tens, whole hundreds, and whole thousand by single digits. It also promotes the correct understanding of knowledge. migration.

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

In the new knowledge exploration session, when the teacher guided the students to explore the algorithm of 3×20=, the students presented three methods: (1) combining the number line with the continuous addition of the same numbers, (2) using List them one by one and discover the rules. (3) By migration and analogy, we can infer from the multiplication in the table to the multiplication of integer tens by one digit, that is, think of 20 as 2 tens, and 3 20s as 6 tens. That is 60. After the exchange of algorithms, the teacher asked students to carefully observe these three methods and think about the connections between these three methods. After independent thinking and group communication, students came to the conclusion that the first method and the second method are essentially the addition of three 20s. The first method is to use the number line to understand, and the second method is to use physical objects (theme map There are three bundles of trees in the tree, and the number in each bundle is 20.) Find the rules to understand. Both methods are to find the number of three 20s. This guides students to communicate the relationship between addition and multiplication well, 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 small number of 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 is better. He just asked: "If you ask for how many roots there are in 9 bundles of saplings, how to calculate them?" This allows students to truly realize that when there are many addends, the third method will be used. The advantages of the three methods are highlighted. Then ask students to complete the textbook "How many trees are there in 4 bundles? What about 5 bundles?". After students complete it independently, ask students to tell you what you think (calculate) and how to calculate (inductive calculation method) ). Let students refine the algorithm: multiply a whole ten number by a single digit. When calculating, first multiply the number by a tens digit, and then add a 0. This guides students to independently generate algorithms based on clear calculation principles.

After students have mastered the arithmetic and algorithm of multiplying integers by one digit, most students can achieve positive transfer when exploring the calculation method of multiplying integers by one digit 3×500= , directly explain the arithmetic: 3 times 500 is to find out what three 500s are, and 3 500s are 15 hundreds, so it is 1500; algorithm: first multiply 5 in the hundreds place by 3 to get 15, and then directly after Add 2 zeros.

Strategy 3: Pay attention to oral arithmetic training and consolidate basic computing abilities.

In the preparation for the review of this lesson, the teacher arranged listening and arithmetic exercises for multiplication in tables, which laid a good foundation for the study of this lesson. After exploring and summarizing the calculation methods, the teacher presented a set of oral arithmetic exercises, allowing students to master the oral multiplication calculation methods of whole tens, whole hundreds, and whole thousand by single digits based on a certain amount of training.

This class does not create overly gorgeous situations, but uses the theme scene pictures in the textbook to carry out teaching; there is no noisy group discussion, only independent thinking without affecting the control of other students. Volume discussion; no exaggerated and excessive praise, only pertinent evaluation after capturing students’ thinking and good habits. The classroom teaching throughout the class was organized and guided by the teacher, allowing teachers participating in the class observation to feel the changes that quietly occurred in the students. Teacher Qin’s simple and efficient mathematics lesson provides a good example for our computing class teaching. ......