The meaning of perimeter:

The length of a closed figure is its circumference.

Methods of measuring the perimeter of the following objects:

1, regular graphics, you can use a ruler to measure the length of each side, and then add up.

2. For irregular figures, you can directly measure the perimeter around the figure with a tape measure, or you can use a rope to wrap around the edge of the figure, and then measure the length of the rope by straightening.

Calculation method of rectangular perimeter:

The circumference of a rectangle is the sum of its four sides. According to the characteristic that the opposite sides of a rectangle are equal, we can first find two lengths and then two widths; You can also find the sum of a length and a width first, and then multiply it by 2, that is, the circumference of a rectangle = length X2+ width X2= (length+width) X2. Then, in turn, the length of a rectangle = perimeter ÷2- width = perimeter ÷2- length.

Calculation method of square perimeter:

The circumference of a square is the sum of the lengths of its four sides. According to the characteristics that four sides of a square are equal, four sides can be added or one side can be multiplied by four, that is, the circumference of a square = side length+side length+side length = side length X4. Then the side length of the square = perimeter ÷4.

Error-prone point:

1, it is easy to make mistakes in finding the perimeter of mosaic. When looking for the perimeter of a mosaic, it is easy to add a middle line segment. When calculating the perimeter of the mosaic figure, it is mistakenly thought that the perimeter of the mosaic figure is equal to the sum of the perimeters of the original figures, so the line segments in the middle of the figure are added up, which leads to the wrong result. When finding the perimeter of a mosaic figure, you can draw a sketch first, find out the line segments outside the figure, and then find the perimeter of the figure. It is easy to make mistakes when solving practical problems in life.

When solving practical problems in life, such as a rectangular vegetable garden, how long the fence needs is still calculated according to the perimeter formula of the rectangle, while ignoring the fence only needs three sides. When solving the problem of rectangle or square, we must first find out how many sides we need. If we want to know the length of a week, we can directly use the perimeter formula.

If you want to sum the lengths of three sides, you can use the perimeter formula to get the perimeter first, and then subtract the unnecessary sides.

Finally, smart memory:

The perimeter formula is very important, and it is needed to calculate the perimeter. Review the questions before the column type, distinguish the figures and find them. Multiply the sum of length and width by 1 and the side length by 4 to find the product.