This topic mainly examines the perimeter of squares and rectangles, and the specific drawing method is as follows:

1. Draw a square with a circumference of 20 cm. According to the formula of square perimeter, the side length of this square is: 20÷4=5 (cm).

2. Draw a rectangle with a circumference of 20 cm. According to the formula of rectangle perimeter, the side length of this rectangle can be: (6+4)×2=20 cm, so it is 6 cm long and 4 cm wide.

Extended data

1. Rectangular perimeter formula: Rectangular perimeter = (length+width) ×2. Because a rectangle has two equal lengths and widths, add the lengths and widths and multiply them by 2 to get the circumference of the rectangle.

2. The formula of the perimeter of a square is: perimeter = side length ×4. Because the four sides of a square are equal in length, the circumference of a square is four times the length of its sides.