【缘起】在完成“长方形和正方形的面积”单元内容教学的最后,为了厘清长方形和正方形的周长与面积的意义、算法以及计量单位,使学生更好地运用长方形和正方形的周长与面积解决实际问题,及时消除相关的知识技能的负迁移影响,教材在练习八专门安排了在同一情境中,长方形或正方形的周长与面积的对比练习。其间,我组织学生练习了这样一道题:比一比,算一算,下面正方形的周长 In order to clarify the meaning, algorithm and unit of measure of the circumference and area of ​​the rectangle and the square, at the end of completing the unit content teaching of “Area of ​​the rectangle and square”, students can make better use of the perimeter of the rectangle and the square With the area to solve practical problems and promptly eliminate the negative transfer of knowledge and skills related to the impact of the teaching materials in practice eight specially arranged in the same situation, rectangular or square perimeter and area of ​​contrast exercises. In the meantime, I organized students to practice such a question: more than one, calculate, the following perimeter of the square