It is not a new mathematical concept, it is related to the length of line segments and curves. A curve, several line segments or several curves plus several line segments can form a perimeter. A certain surface of an object or a closed plane figure (regular or irregular) has a perimeter, while a non-closed figure has no perimeter.

The perimeter of each figure: the perimeter of a rectangle = (length+width) x2, that is, c=2(a+b)(c is the perimeter, a is the length, and b is the width). According to the characteristics that all four sides of a square are equal, it is concluded that the circumference of a square is equal to the side length x4, that is, C is equal to 4a (c is the circumference and A is the side length).

According to the relationship between the circumference and the diameter of a circle, it is concluded that the circumference of a circle = the diameter xπ(π), that is, c= πd= 2πr(c is the circumference, d is the diameter, and r is the radius). Find the perimeter (the formula must be memorized) The perimeter of the parallelogram is calculated by the rectangular formula: the perimeter of the parallelogram = (length+width) ×2.

Note: The length of the perimeter has nothing to do with the shape of the figure. The perimeter of a square is related to the side length, and the perimeter of a rectangle is related to the length and width. Find the perimeter of the puzzle. In solving problems, when finding the perimeter of a rectangle, we should first look at whether the units of length and width are consistent.

For example, a rectangular sports field is 20 meters long and 10 meters wide. What is the circumference of this playground? {Rectangular perimeter = (length+width) ×2}(20+ 10)×2=60 (meters).