What is the length of the closed shape?

Perimeter refers to the length of the closed graphic boundary, which can also be understood as the length of "walking around the graphic". Perimeter is suitable for various shapes, including rectangle, circle, triangle and so on. The unit for calculating the circumference is usually the length unit, such as meters, centimeters, feet, etc.

For simple shapes, such as rectangles and squares, the perimeter can be obtained directly by adding the side lengths. As shown in the figure below, the mobile phone case is approximately rectangular, so its perimeter is "walking around the figure", that is, the length of the red rectangle.

For more complex shapes, it can be calculated by decomposing the shape into simple shapes. For example, the three sides of a triangle are 3 meters, 4 meters and 5 meters respectively, and the circumference of 12 meter can be obtained by adding these three sides.

In a word, the perimeter is the length of the closed graphic boundary, which can be used to calculate the size of various shapes. Through appropriate formulas and calculation methods, we can easily calculate the perimeters of various shapes.