《九年义务教育小学数学教学大纲》指出：“要遵循学生的认知规律，重视学生获取知识的思维过程，通过操作、观察，引导学生进行比较、分析、综合，在感性材料的基础上加以抽象概括，进行简单的判断、推理。”从心理学观点来看，儿童认识事物是从感知开始然后形成表象，由表象 “Nine-year compulsory education primary school mathematics syllabus” states: “Students should follow the law of cognition, emphasis on students thinking process of acquiring knowledge, through the operation, observation, guide students to compare, analyze, synthesize, on the basis of perceptual material Abstract summary, simple judgment, reasoning. ”From a psychological point of view, children recognize things from the perception and then the formation of the image from the appearance