【课前思考】《认识图形的周长》是浙教版三年级上册的内容,是学生在数学学习中第一次系统地接触“周长”这个概念。这部分内容是在学生对线段的长度概念和度量单位有了一定认识,并且具备了测量线段和计算总和以及熟悉了三角形、平行四边形、长方形、正方形等平面图形的基础上展开的,这是学习平面图形周长的基础。学生只有对周长的概念做到真正的理解,才能对周长的测量、计算及应用有更好的理解认识。教材 “Thinking before class” “Understanding the perimeter of graphics” is the content of the third grade of Zhejiang Education Publishing House, which is the first time that students have systematically contacted the concept of “circumference” in mathematics learning. This part of the content of the students in the length of the line concept and unit of measure have a certain understanding, and have the measurement line and calculate the sum and familiar with the triangle, parallelogram, rectangle, square and other plane graphics based on the development, it is learning The basis of the graphic perimeter. Students only have a true understanding of the concept of perimeter, in order to have a better understanding of perimeter measurement, calculation and application. Teaching material