新《数学课程标准》指出：数学教学活动必须建立在学生的认知发展水平和已有的知识经验基础之上。教师应激发学生的学习积极性，向学生提供充分从事数学活动的机会，帮助他们在动手实践、自主探索和合作交流的过程中真正理解和掌握基本的数学知识与技能、数学思想与方法，获得 The new “Mathematics Curriculum Standard” points out: Mathematics teaching activities must be based on the level of cognitive development of students and the existing knowledge and experience. Teachers should stimulate students' enthusiasm for learning and provide students with opportunities to fully engage in math activities so as to help them to understand and master basic math knowledge and skills, mathematical ideas and methods, and obtain them in hands-on practice, self-exploration and cooperation and exchange.