"Collection" is the content of Unit 9 "Mathematics Wide Angle" in the first volume of the third grade of primary school mathematics published by People's Education Press. Through the study of this lesson, students can understand the meaning of the concept of set and related calculations, and learn to solve simple practical problems with the thinking method of set. As one of the basic ways of thinking in mathematics, set thinking is also a mathematical thought that people often use in their study and life.

Junior three students have already known the consciousness of "overlap" and "combination of numbers and shapes", but they still lack the experience of solving practical problems with mathematical knowledge.