The collection is the content of the first volume of mathematics in the third grade of People's Education Press, Mathematics Wide Angle. It used to be called "overlapping problem", but now the textbook has changed it into "set" It is the basis for children to learn and collect in the future.

In the teaching process of this lesson, we all learn the set problem with the "set diagram" as the carrier.

Firstly, the table with repeated information is displayed, and the repeated information is extracted, and then the table information is converted into a set diagram. Then solve the problem through the set diagram.

We want to visualize the information through the set diagram, which is conducive to children's understanding.

But the reality is that children can't control the whole process in class.

Because in this course, children's thinking needs to go through five steps: generating set diagram, presenting text information in the form of set diagram, reading set diagram, drawing set diagram and solving problems. Every link is brand new to children. So the children won't agree. Finally, directly ignore the first four links and go straight to the "theme"-directly solve the problem. A class that should be permeated with fixed thinking has become a problem-solving class.