(一)比较大小,探索方法
1.小组合作,探究方法
师提出:要想知道哪个国家的陆地面积最大,哪个国家的陆地面积最小,怎么办?你想怎样比较?请在小组内说一说你的比较方法。
2.全班交流,方法
师组织学生进行全班交流,学生可能根据数位的多少来比较,可能根据分级来比较,也可能根据数的组成来比较,还可能借助一个标准数来比较……。
对不同的比较方法老师都应给予鼓励与肯定,让学生体验解决问题策略的多样性。
3、优化方法
师提出:你认为哪种方法最简便,使用起来最快捷?(学生各抒已见)
4、归纳总结
师小结:我们在进行比较时就可以用同学们研究的既快捷又方便的方法。就是可以先看一看这些数分别是几位数,位数多的那个数就大,位数少的那个数就小;如果位数相同,就从最高位开始比较,最高位大的那个数就大,如果第一位相同就看一下位,以此类推。
5、巩固练习:比较下面每组中的两个数的大小
(二)、改写整万、整亿数为“万”或“亿”做单位的数
1、写数,体会改写的必要性
(1)师出示如下信息并要生写出横线上的数,在交流展示写的.结果时,先让学生起来读一读写出的数,通过读数让学生知道这两个数分别是整万数和整亿数。
接着提出:在刚才写的过程中,你有何体会?那么有没有写起来简便、读起来快捷,并且不改变原数大小的写法呢?同桌说一说你有什么好方法?
(学生可能会交流:用汉字代替阿拉伯数字)
师提出:那么我们就以“万”或“亿”为单位表示我国的陆地面积与人口总数,小组交流说一说怎样改写?
(2)全班交流
根据学生的回答,教师板书:
9600000平方千米=960万平方千米
1300000000人=13亿人
师提问:在将整万或整亿的数改写成“万”或“亿”作单位的数时,应该怎样改写?
交流后引导学生得出以下结论:
把整万数改写成以“万”为单位的数,可以先分级,再把万位后面的4个0去掉,最后添上一个“万”字。
把整亿数改写成以“亿”为单位的数,同样要先分级,再把亿位后面的8个0去掉,最后添上一个“亿”字。
2、对比观察,感受改写的简洁性。
师提问:比较两种写法,你认为哪种方法更简便?
通过对比各个等式的左右两边,学生很容易地感受到改写后的简洁性。
3、巩固练习:把下面的数改写成用“万”或“亿”作单位的数
Children's finally here, it is our holiday, but imagine the children also accompanied by together, everybody is more excited.
Children on this day, white clouds float over the blue sky, the children also have made a hot air balloon, they sit together on yourself a hot-air balloon, extremely happy! Balloon flying high, and finally flew to the sky, the children are in the sky holiday, the children sit on clouds, umpa jump, like a frisky little monkey.
Playing children, suddenly to rain cats and dogs, the children of the balloon has stalled, baiyun sister swept away by the wind, the children fell into despair. Is a time of crisis, a group of dragonflies sister and sister flew caught the children, and the safety of the children to the ground.
On the ground, only butterflies woven into a rainbow "lei", the children wear a wreath, some like a fairy, some like a warrior.
Play tired, the children fell asleep between full of fragrance of flowers.
Children's good play my imagination, to one day be able to live in such a children's day.
7.(1)特别爱好(或“喜欢”、“爱好”)
(2)跑
(3)率领(或“带领”)
(4)适逢,正赶上
(评分说明:每小题1分,共4分)
8.(1)因此人家大多数愿意把书借给我,我于是能够读到各种各样的书籍。(关键词:以是以因遍观)
(2)(他)常常独自在庭院(台阶)散步,说:“古人难道在欺骗我吗(或古人怎么能欺骗我呢)?”(关键词:恒步岂和省略句每一点0.5分)
(评分说明:每小题2分,共4分)
9.抄书治水失败
10、(1)示例:刘羽冲是一个喜欢读书但做事不切实际的人。他虽然潜心研读古代的兵书和水利书,但不能灵活地运用于实际之中,结果屡遭失败,抑郁而死。
(2)言之成理即可
掌握万以上数的大小比较的方法,学会大数的改写。
教学流程大致如下:
What our life will be like in the future?When I was a little boy,I always asked myself this question.At that time,I had no idea what Internet was.But now,we use it every day.We can't live without it.Internet is become so popular and so convenient.
Just forget it.What our life will be like in the future?For example,in ten years.I think that in ten years our life will be much more colorful,our computer will be much powerful,and we can do almost everything on the internet including seeing a doctor.What about your future life ?Will you share with me?
The fox, filled with arrogance, examined the cat from head to feet, and for a long time did not know whether he should give an answer. At last he said, "Oh, you poor beard-licker, you speckled fool, you hungry mouse hunter, what are you thinking? Have you the nerve to ask how I am doing? What do you know? How many tricks do you understand?"
"I understand but one," answered the cat, modestly.
"What kind of a trick is it?" asked the fox.
"When the dogs are chasing me, I can jump into a tree and save myself."
"Is that all?" said the fox. "I am master of a hundred tricks, and in addition to that I have a sackful of cunning. I feel sorry for you. Come with me, and I will teach you how one escapes from the dogs."
Just then a hunter came by with four dogs. The cat jumped nimbly up a tree, and sat down at its top, where the branches and foliage completely hid her.
"Untie your sack, Mr. Fox, untie your sack," the cat shouted to him, but the dogs had already seized him, and were holding him fast.
"Oh, Mr. Fox," shouted the cat. "You and your hundred tricks are left in the lurch. If you been able to climb like I can, you would not have lost your life."
一只猫在森林里遇到一只狐狸,心想:“他又聪明,又丰富,挺受人尊重的。”於是它很友好地和狐狸打招呼:“日安,尊敬的狐狸先生,您好吗?这些日子挺艰难的,您过得怎么样?”
狐狸傲慢地将猫从头到脚地打量了一番,半天拿不定主意是不是该和它说话。最后它说:“哦,你这个倒霉的长着鬍子、满身花纹的傻瓜、饥肠辘辘地追赶老鼠的.傢伙,你会啥?有甚么资格问我过得怎么样?你都学了点甚么本事?”
“我只有一种本领。”猫谦虚地说。
“甚么本领?”狐狸问。
“有人追我的时候,我会爬到树上去藏起来保护自己。”
“就这本事?”狐狸不屑地说,“我掌握了上百种本领,而且还有满口袋计谋。我真觉得你可怜,跟着我吧,我教你怎么从追捕中逃生。”
就在这时,猎人带着四条狗走近了。猫敏捷地窜到一棵树上,在树顶上蹲伏下来,茂密的树叶把它遮挡得严严实实。
“快打开你的计谋口袋,狐狸先生,快打开呀!”猫冲着狐狸喊道。可是猎狗已经将狐狸扑倒咬住了。“哎呀,狐狸先生,”猫喊道,“你的千百种本领就这么给扔掉了!假如你能像我一样爬树就不至於丢了性命了!”
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