X represents the largest integer not exceeding X. On the number axis, it represents the integer closest to X on the left. When X is an integer, X is itself. Integer function x is also often called floor. Because it doesn't exceed X, and it is the closest to X, just like the floor under our feet. Mathematics originates from life and is higher than life at the same time. For primary and middle school students, mathematics should help them solve mathematical problems in daily life or explain some phenomena in real life. This will make them feel that mathematics is not only an empty theory, but also useful, thus enhancing their interest in learning mathematics. The functions of ceiling and floor are widely used in real life. For example, the problem of riding in real life: according to the total number of people and the maximum number of people each car can carry, the number of vehicles used can be calculated. When the calculation result is an integer, it can be rounded directly. If it is not an integer, ask students to know how to take an extra car according to their daily experience. This is an application of the ceiling function. When shopping in real life, sometimes the fraction of the price is removed because of bargaining. This is actually an application of floor function or disguised floor function. These mathematical problems abstracted from practical problems, such as the ceiling function and floor function above, are actually as easy to be accepted by students as rounding and discount rate.