“长方形、方形和平行。边形。是小学数学第五册第五单元的教学内容。它包括长方形和正方形的特征，平行四边形的初步认识，周长的含义和长方形、正方形周长的计算。教学重点是长方形、正方形周长的计算，教学难点是建立周长的概念。教学这一部分内容要让学生主动参与，通过动 "Rectangle, Square and Parallel. The polygons are the teaching content of the fifth unit of elementary school mathematics fifth volume, which includes the characteristics of rectangular and square, the initial understanding of parallelogram, the meaning of perimeter and the calculation of rectangle and square perimeter. Teaching focuses on the calculation of the rectangle and the perimeter of the square, and the difficulty in teaching is to establish the concept of the perimeter. The part of teaching is for the students to participate actively.