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    方仁055主页 >> 文章 >> 课堂随想 >> 浏览信息《创设情境  自然引入》

    课堂随想 | 评论(1) | 阅读(625)
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    星期三   晴天 
    主题 创设情境  自然引入

    创设情境  自然引入 

     

    ——听顾建新老师执教《异分母分数加减法》一课有感

     

    兴化市楚水小学  於以华

     

    428日,楚水小学数学组举行听课教研活动。顾建新老师为全校数学老师执教了五年级《异分母分数加减法》一课。这个这节课,顾老师精心创设情境引导学生自主探究异分母分数加减法的计算方法,取得了较好的教学效果。听课后我特别对顾老师创设情境自然引入新课这一环节印象深刻,应该说本节课取得了较好的教学效果与这个环节的处理十分到位有着密切的关系。现就这一环节作简单评析与思考

     

    教学片段:

     

    师:你能用分数表示下列图形中的阴影部分吗?(课件出示图形)

     

    生:(准确说出每题答案)

     

    师:你能把任意2个图形的阴影部分合起来,用算式表示出来吗?

     

    生:第2幅图和第4幅图的阴影部分合起来算式是1/4 +2/4

     

    生:第3幅图和第5幅图的阴影部分合起来算式是3/8 +4/8

     

    生:第1幅图和第4幅图的阴影部分合起来算式是 1/2+ 1/4

     

    生:第2幅图和第5幅图的阴影部分合起来算式是 1/4+ 3/8

     

    生:第4幅图和第5幅图的阴影部分合起来算式是 2/4+ 3/8

     

    ……

     

    师:(师有选择地将算式板书成2类)你觉得怎样给这些算式分分类呢?

     

    生:同分母的算式算一类,异分母的算式算一类。

     

    师:什么是同分母的算式呢?它们有哪些?其他呢?

     

           生:分母相同的分数加法算式是同分母的算式,它们有1/4 +2/43/8 +4/8 ,其他的都是异分母加法的算式。

     

    师:3/8 +4/8 你们是怎么思考的?

     

           生:3/8 +4/8是同分母分数加法,他们的分数单位相同都是1/8,4/8就是4个1/8,3/8就是3个1/8,合起来一共有7个1/8,就是7/8

     

    师:对,相同的分数单位我们才可以相加,这是我们以前学习过的……

     

    生(齐):同分母分数加法。

     

    师:同分母分数加法的计算法则是……

     

    生:分母不变,分子直接相加。

     

    师:同分母分数减法呢……

     

    生:分母不变,分子直接相减。

     

    (指着异分母加法这一类算式):这些是……

     

    生(齐):异分母分数加法。

     

    师(板书并揭题):异分母分数加  法(留下“减”的空当,为下面完整板书打下伏笔)。

     

    评析思考:

     

    课程标准指出:“要创设与学生生活环境、知识背景密切相关的,又是学生感兴趣的学习情境,让学生在观察、操作、猜测、交流、反思等活动中逐步体会数学知识的产生、形成与发展的过程,获得积极的情感体验,感受数学的力量,同时掌握必要的基础知识与基本技能”。

     

    顾老师的引入正是遵循了这样的理念:让学生从简单的用分数表示阴影部分的面积填写起,设计开放的问题引导学生自然地说出同分母分数的加法和异分母分数的加法这两类不同的算式;教师适时的选择板书成两类,引导学生准确自然地分类:同分母加法和异分母加法;在叙述同分母分数加法的计算法则的同时补充同分母分数减法的计算法则,并自然地引入课题——异分母分数加法。这样的情境创设来源于学生的已有知识基础:用分数表示阴影部分的面积是五年级刚学过的内容,分数(包括同分母和异分母)加法算式来自于学生的口述,分类的精确结果也源于学生的算式,同分母分数加减法的计算法则复习也显得水到渠成。

     

    同样这样的引入还为下面的自主探究打下伏笔:异分母分数加法的算式来源于学生的口述,既为学生的自主探究提供了良好的素材,同时又调动了学生学习的积极性——探究的问题来源于自己的发言;用分数表示图形的阴影部分暗藏着把异分母分数通分的启示;异分母分数加法也要是相同的分数单位才可以相加;课题中的留白预示着……

     

    马云鹏教授说过:“好的数学课是自然流淌的课”。顾老师的引入就是这样的,在简洁中显得清晰、流畅,水到渠成,同时在简洁中蕴含着课堂的内在品质和价值追求——锻炼学生的数学思维,丰富儿童的学习情感,达成全面的课堂目标,彰显老师的教学智慧。

     

     

     

     

    方仁055 发表于:2011-5-11 18:36:42

    评论 

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