认识大于小于和等于.doc

认识大于 小于和等于
教 案 首 页
教学 授课 课题 认识“,”、“,”和“,” 主备人 何银 1
课时 时间
学习 对生活中的直观事物进行比较 基础
学 情
分
析 学习
困难,、,的掌握及应用
预测
例题提供了童话场景“森林运动会”，从不同动物只数的比较中，抽象出数
学的大小关系。比较两种物体数量的多与少，基本方法是一一对应。教材先教 引导学生比较森林运动会上小兔和小猴的只数。通过一一对应的排列让学生材 明确他们的只数相同，以此建立“同样多”的概念。在此基础上，抽象出“4分 ,4”认识并理解“,”的含义。接着引导学生比较运动会上松鼠和小熊的析 只数，通过一一对应的排列，使学生明确松鼠只数比小熊多，小熊只数比松
鼠少，从而建立“多”“少”的概念，再抽象出“5,3” “3,5”，认识理
解“,”“,”的概念。
课
标 理解符号,，,，,的含义，能用符号和词语描述万以内数的大小。 要
求
教 1、会读、写“,，,，,”，并知道他们的意义，会用它们表示数的大小。 学 2、学生在喜爱的故事情境中操作，知道用一一对应的方法来比较物体的多目 少。 标 3、培养学生的观察力、参与意识和创新精神。
教
学 学生认识“,” “,” 和“,”这三种符号及其含义。 重
点
edges should be cleaned, after making sure that no defect shall be marked with a marker pen to write down welding near the weld, including the slogan of welding, welders, etc. (16) welding Qian Preheat and the welding Hou heat treatment pipe welding Qian Preheat and the welding Hou heat treatment process conditions welding Qian Preheat and the welding Hou heat treatment temperature table project material welding Qian preheat temperature (?) welding Hou heat treatment and the insulation time (?/H) wall thick (mm) temperature (?) wall thick (mm) temperature (?) 20 ? 26 100~200 >36 600~650/1- 15CrMo ? 10 150~200 >10 670~700/-2 Preheat and the heat treatment process in the, Inner and outer wall temperature shall be kept uniform, in order to avoid internal stresses. Preheating before welding and post weld heat treatment, shall measure and record the temperature, temperature measurement locations and number of points are reasonable. Prone to weld delayed crack of steel, post weld heat treatment after welding should be carried out promptly, when not conducting timely post weld heat treatment, should be uniformly heated to 200~300? immediately after welding and insulation and slow cooling, ... 26mm more than 20 steel pipe welding preheating before welding should be carried out, 36mm the above heat treatment after welding should be done. Before welding and heat treatment used oxyacetylene flame heating, h