2019年沪教版四年级上册数学教案:《四舍五入法(第1课时)》

2019-09-24 17:27:00来源:网络

  从学生已有的知识、经验出发,即从估算、凑整引入,在复习旧知的基础上为新知学习作好铺垫。

  二、核心推进过程

  (一)相邻的整万数。

  1.写出与a、b、c、d相邻的整万数,在最接近它的整万数上画“√”。

  

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" width="317" height="84"/>

  (1)写一写:它们分 别接近哪两个整万数?

  (2)并写出相应的整万数。

  (3)说一说:它们分别最接近哪个整万数?你是怎么想的?

  2.写出与下列各数相邻的整万数,在最接近它的整万数上画“√”。

  

\

  (1)试写出与24975相邻的整万数。

  (2)组织学生讨论:如何找到与它最接近的整万数?

  (3)写一写:与325841 、7893201相邻的整万数。

  (4)引导学生归纳:如何 找出与一个数最接近的整万数?

  (5)口答:说出与下列数最接近的整万数,并说明理由。

  36937 872098

  (二)相邻的整十万数。

  1.以上题中“872098”为例:

  (1)写一写:它接近哪两个整十万数?并写出 相应的整十万数。

  (2)说一说:它最接近哪个整十万数?你是怎么想的?

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