【本案背景】这是北师大版数学二年级下册第55～57页的教学内容。日常生活中解决实际问题往往不一定要精确的结果,只要知道得数大约是多少就可以了,这就需要估算。教材认真落实《标准》“不失时机地培养学生的估计意识和初步的估计技能”的要求,在教学笔算的同时也教学估算。教学估算并不是把估算方法直接告诉学生,而是在现实情境中激活学生已有的估计经验,自己探索估算方法。让学生亲身经历探索加法估算方法的过程,理解并学会加法估算方法,并通过估算练 【Background】 This case is the second edition of the second edition of Beijing Normal University Volume 55 ~ 57 teaching content. To solve practical problems in daily life often do not have to be accurate results, as long as you know how much is about it, which requires estimation. Teaching materials Seriously implement the “standard” “seize the opportunity to cultivate students’ awareness of the initial estimation skills and ” requirements, teaching pen calculation at the same time teaching estimates. Teaching estimation does not tell the students directly about the estimation method. Instead, it activates the students’ existing estimation experience in realistic situations to explore the estimation methods themselves. Allow students to experience the process of exploring additive estimation methods, understand and learn additive estimation methods, and by training