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    秦仕祥主页 >> 文章 >> 教学论文 >> 浏览信息《末尾有0的乘法练习》

    教学论文 | 评论(1) | 阅读(892)
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    星期一   晴天 
    主题 末尾有0的乘法练习

    教师:秦仕祥                           总第     课时

     

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                
                

                

     

                

                
                

    末尾有0的乘法练习            

     

                

                
                

    课时            

     

                

                
                

    4            

     

                

                
                

    授课时间            

     

                

                
                

                

     

                

                
                

                

     

                

                

                

     

                

                
                

    1、使学生进一步力和掌握末尾有0的乘法笔算方法,并能正确熟练地进行计算。

                

    2、培养学生细心计算、认真书写的计算习惯。

                
                

                

     

                

                

                

     

                

                
                

    积与乘数的变化规律。

                
                

                

     

                

                

                

     

                

                
                

    小黑板

                
                

    板书            

     

                

                

    设计            

     

                

                
                

    一个乘数不变,另一个乘数扩大(或缩小)多少倍,积也随着扩大(或缩小)相同的倍数。

                
                

                

     

                

                

                

     

                

                
                

                

     

                

                
                

    教师活动内容、方式            

     

                

                
                

    学生活动内容、方式            

     

                

                
                

                  

     

                

                
                

    一、训练            

     

                

                

    口算:第6页的第7题。

                

    二、计算下面各题

                

       840×64     760×40     4800×320

                

       重点评讲4800×320,这是一道拓展题,引导学生研究:最后添三个0,为什么?

                

    三、研究乘数与积的变化规律

                

      1、逐步出示数据

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
                            

    乘数

                            
                            

    14

                            
                            

    14

                            
                            

    14

                            
                            

    14

                            
                            

    14

                            
                            

    ……

                            
                            

    乘数

                            
                            

    2

                            
                            

    20

                            
                            

    200

                            
                            

    2000

                            
                            

    20000

                            
                            

    ……

                            
                            

                            
                            

    28

                            
                            

    280

                            
                            

    2800

                            
                            

    28000

                            
                            

    280000

                            
                            

    ……

                            
                

    14×2等于多少?            

     

                

                

    (算出第二组的积)第二组数据与第一组数据比较,有什么相同点?有什么不同点?            

     

                

                

    板书:第一个乘数不变,第二个乘数扩大10            

     

                

                

    积怎么变化?            

     

                

                

       板书:积也扩大10            

     

                

                

    (算出第三组的积)第三组数据与第一组比较,有什么相同点?有什么不同点?积怎么变化?            

     

                

                

    板书:第一个乘数不变,第二个乘数扩大100倍,积也扩大100倍。            

     

                

                

    (算出第四组的积)第四组数据与第一组比较,有什么相同点?有什么不同点?积怎么变化?            

     

                

                

    板书:第一个乘数不变,第二个乘数扩大1000倍,积也扩大1000倍。            

     

                

                

    (算出第五组的积)第五组数据与第一组比较,有什么相同点?有什么不同点?积怎么变化?            

     

                

                

    板书:第一个乘数不变,第二个乘数扩大10000倍,积也扩大10000倍。            

     

                

                

    如果第一个乘数不变,第二个乘数扩大100000倍,积又怎么变化?            

     

                

                

    以此类推还可以得到什么结论?            

     

                

                

    从这里发现什么规律?            

     

                

                

    板书:第一个乘数不变,第二个乘数扩大多少倍,积也扩大相同的倍数。            

     

                

                

    2反过来研究得出:

                

    第四组与第五组比较,两乘数有什么变化?积呢?

                

      得出:第一个乘数不变,第二个乘数缩小10倍,积也缩小10

                

    第三组与第五组比较,两乘数有什么变化?积呢?

                

      得出:第一个乘数不变,第二个乘数缩小100倍,积也缩小100

                

    第二组与第五组比较,两乘数有什么变化?积呢?

                

        得出:第一个乘数不变,第二个乘数缩小1000倍,积也缩小1000

                

    第一组与第五组比较,两乘数有什么变化?积呢?

                

         得出:第一个乘数不变,第二个乘数缩小10000倍,积也缩小10000

                

    由此又得到什么规律?

                

    板书:第一个乘数不变,第二个乘数缩小多少倍,积也缩小相同的倍数。            

     

                

                

    到现在我们已经学习了几个规律?哪两个规律?可以合并起来说吗?            

     

                

                

    合并成:第一个乘数不变,第二个乘数扩大(或缩小)多少倍,积也随着扩大(或缩小)相同的倍数。            

     

                

                

    3逐步出示下面数据            

     

                

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            
                            

    乘数                        

     

                            

                            
                            

    14                        

     

                            

                            
                            

    140                        

     

                            

                            
                            

    1400                        

     

                            

                            
                            

    14000                        

     

                            

                            
                            

    140000                        

     

                            

                            
                            

    ……                        

     

                            

                            
                            

    乘数                        

     

                            

                            
                            

    2                        

     

                            

                            
                            

    2                        

     

                            

                            
                            

    2                        

     

                            

                            
                            

    2                        

     

                            

                            
                            

    2                        

     

                            

                            
                            

    ……                        

     

                            

                            
                            

                            

     

                            

                            
                            

    28                        

     

                            

                            
                            

    280                        

     

                            

                            
                            

    2800                        

     

                            

                            
                            

    28000                        

     

                            

                            
                            

    280000                        

     

                            

                            
                            

    ……                        

     

                            

                            
                

    ⑴(先算出第12组的积)第二组与第一组比较,两个乘数有什么变化?积呢?            

     

                

                

    得出:第二个乘数不变,第一个乘数扩大10倍,积也随着扩大10倍。            

     

                

                

    ⑵(先算出第12组的积)第二组与第一组比较,两个乘数有什么变化?积呢?            

     

                

                

    ⑶(先算出第3组的积)第三组与第一组比较,两个乘数有什么变化?积呢?            

     

                

                

    得出:第二个乘数不变,第一个乘数扩大100倍,积也随着扩大100倍。            

     

                

                

    ⑷(先算出第45组的积)分别与第一组比较,两个乘数有什么变化?积呢?            

     

                

                

    你又发现了什么规律?            

     

                

                

    得出:第二个乘数不变,第一个乘数扩大多少倍,积也随着扩大相同的倍数。            

     

                

                

       反过来研究            

     

                

                

    得出:第二个乘数不变,第一个乘数缩小多少倍,积也随着缩小相同的倍数。            

     

                

                

    把两个规律合并起来            

     

                

                

    第二个乘数不变,第一个乘数扩大(或缩小)多少倍,积也随着扩大(或缩小)相同的倍数。            

     

                

                

    4到现在为止我们一共研究出了几个规律?这四个规律能合并吗?怎么合并?            

     

                

                

    概括出:一个乘数不变,另一个乘数扩大(或缩小)多少倍,积也随着扩大(或缩小)相同的倍数。            

     

                

                

                

     

                

                

                

     

                

                

    4、练习            

     

                

                

    6页第68910教师组织评讲。

                
                

                

     

                

                

    学生集体口答得数

                

                

     

                

                

    学生计算,研究得出:48个百乘32个十等于1536个千,所以添三个0

                

                

     

                

                

                

                                                                                                                
                            
                            

    4  4

                            

    × 1  5

                            

    2  2  0

                            

    4  4

                            

    6  6  0

                            
                            
                                                                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                
                

    教师提问、学生思考,逐步得出结论,最后归纳出:

                

    第一个乘数不变,第二个乘数扩大多少倍,积也扩大相同的倍数。

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

    教师提问、学生思考,逐步得出结论,最后归纳出:

                

    第一个乘数不变,第二个乘            

     

                

                

    数缩小多少倍,积也缩小相同的倍数。            

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

    学生先独立思考,再交流,最

                

    后概括出:

                

    第一个乘数不变,第二个乘数扩大(或缩小)多少倍,积也随着扩大(或缩小)相同的倍数。            

     

                

                

                

     

                

                

                

     

                

                

    教师提问、学生思考,逐步得出结论,最后概括出:

                

    第二个乘数不变,第一个乘数扩大多少倍,积也随着扩大相同的倍数。

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

    教师提问、学生思考,逐步得出结论:第二个乘数不变,第一个乘数缩小多少倍,积也随着缩小相同的倍数。

                

                

     

                

                

    教师提问、学生思考,逐步得出结论。概括出:            

     

                

                

    一个乘数不变,另一个乘数扩大(或缩小)多少倍,积也随着扩大(或缩小)相同的倍数。            

     

                

                

                

     

                

                

    学生练习。

                
                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                
                

                

     

                

                

                

     

                

                

                
                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

                

     

                

                

     

    秦仕祥 发表于:2012-2-20 21:13:42

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