The first volume of grade four is an important chapter in mathematics, numbers and graphics. The purpose of this chapter is to lay the foundation for junior high school to learn plane geometry and senior high school to learn solid geometry. The study of mathematics and graphics in the basic stage is very important, just like the "foundation" of building a house. The first volume of mathematics and graphics in the fourth grade is also of great significance to cultivate the concept of space and develop the ability of logical thinking.