Teacher: What information have you collected from the statistics?
Students 1: 8 people join the Chinese interest group and 9 people join the math interest group.
Student 2: Some students take part in both Chinese interest groups and math interest groups.
S3: The number of people participating in interest groups in Chinese and Mathematics is not 17.
2. Group discussion.
How many people in Class Three (1) are interested in Chinese and math?
Students 1: two groups 17 people. Because there are 8 people in the Chinese interest group and 9 people in the math interest group. 8+9= 17 (person)
Student 2: There are no 65,438+07 people in the two groups. Some students have joined the two groups themselves, so they can't count any more.
S3: There are 14 people in two groups. Because three students, Yang Ming, Li Fang and Liu Hong, participated in the Chinese interest group and the math interest group at the same time, they can't count any more. They are 8+9-3= 14 (people).
The students argued in the discussion. Teacher: Now let's divide the names of the two groups of students into two groups as required.
First, students draw a circle in the exercise book, fill in the corresponding student names, and then report and present a student's exercise with multimedia.
Teacher: What do these two pictures mean?
Student: On the left is a Chinese interest group of 8 people, and on the right is a math interest group of 9 people.
Teacher: What else do you find from these two circles?
Health 1: Yang Ming, Li Fang and Liu Hong have names in the left circle and the right circle.
Health 2: You can erase the names of these three people in the left circle or the right circle.
S3: If the names of these three people are erased from the left circle, aren't there three people missing from the Chinese interest group? Or, if the names of these three people are erased from the right circle, aren't there three people missing from the math interest group?
Student 4: Cross these two circles, and write the names of the students who have participated in the Chinese group and the math group in the cross circle.
According to the students' answers, the teacher displays on the multimedia screen: gradually merge the two circles and put the names of three students in the crossed circles.
Teacher: Tell me the meaning of different positions.
Students: The five people on the left only join the Chinese interest group, the three people in the middle cross section join the Chinese interest group and the math interest group at the same time, and the six people on the right are students who only join the math interest group.
Teacher: How many people have joined the Language and Numbers Interest Group? How do you count it?
Student 1: 8+9-3 = 14. Because three people have joined both the Chinese interest group and the math interest group, they can't count any more, so they are subtracted.
Student 2: 5+3+6 = 14, because five people join the Chinese interest group, three people join the Chinese and math interest groups at the same time, and six people only join the math interest group, so these three parts add up to the number of people.
Student 3: 8+6 = 14, because there are 8 people in the left circle who participated in the language interest group, and 3 of them participated in the language interest group, so there are only 6 people on the right. ...
Reflecting on the idea of set is one of the basic ideas of mathematics. Since students began to learn mathematics, in fact, they have been using the set thinking method. In the teaching clip, the teacher asked the students to write down the names of two interest groups in two assembly circles respectively. After the students finished writing, every student was seriously thinking about how to deal with these three duplicate names.
In order to realize effective inquiry, teachers must provide students with opportunities for full cooperation and communication. In cooperation and communication, underachievers can get the help and guidance of gifted students, middle students can confirm whether their thinking is correct, and top students can gradually improve themselves in communication, thus making their inquiry more perfect, rational and scientific. For example, through the cooperation and communication in the teaching clips, most students can understand that the objects with double sets of values like "two …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… During the discussion and communication, students' thinking collided many times, which not only made them deeply understand the diversity of algorithms, but also provided greater possibilities for students' rigorous thinking and intellectual development. (Author: Shuinan Mingde Primary School, suichuan county, Jiangxi)
□ Editor Deng Shengyuan
E-mail: jxjydys @126.com.