用字母表示数教案.doc

to clean and repair, it is strictly forbidden to head reaches into the mechanical stroke range. 17th article: in overhead transmission line following work should blackout, cannot blackout Shi, due isolation protection measures, crane shall not in overhead transmission line following work, through overhead transmission line should will lifting arm falls, in overhead line side work Shi, regardless of in any situation Xia, lifting arm, and rope or weights, and overhead transmission line of recently distance should not is less than Xia table provides: transmission line voltage 1000 v following 1-15 kV 20-40 kV 60-110 kV 220,000 v Allow minimum distances with the transmission line (m) vertical 1.5 level 1 1.5 2 3 4 5 6 4 6 18th: lamp voltage may not exceed 36 volts, when working in a damp place or metal containers, lamp voltage may not exceed 12 volts. 19th: pressure vessel should have a safety valve, pressure gauge, and avoid sun exposure, collisions, oxygen cylinders to prevent contaminated oil; of acetylene gas, LPG, must have a safety device to prevent tempering. 20th: x-ray and gamma-ray flaw detector operation area, non-operator, not allowed to enter. Article 21st: corrosion, dust and radioactive and toxic work, protective measures are required, and to carry out regular inspection. Spider-man 22nd section III: Spider-man to regular medical examinations of the medical diagnosis, who suffer from high blood pressure, heart disease, anemia, epilepsy and other discomfort in the Spider-man shall not engage in aerial work. 23rd: Spider-man dressed spirit, banned the wearing of hard bottom and easy slip-on shoe nail. 24th: Spider-man material stack stationary, tools should turn into a tool bag, transfer prohibited throwing of objects. 25th: in case of bad weather (such as wind in the above grade) construction safety, prohibition of the open air, lifting and piling. 26th article: ladder shall not deficiency document, no padded using, ladder cross document spacing to 30 cm suitable, using Shi top to tied prison, bottom should take anti-sliding measures, single ladder and ground angle to 60 degrees suitable, ban II people while in ladder Shang job, as needed received long using, should lashing firm, people Word ladder in end of feet pulled prison, in channel at using ladder, due guardianship or set fence. 27th: no security measures, prohibited in hip joints, supports, trusses of the roof truss cantilever beams, and choose the frame and half fixed widget or job to walk on, Spider-man and the ground . Nine, ten basic security to prevent vehicle damage claim 1, without legal training of qualified certified personnel not familiar with vehicle performance is not driving a car. 2, should insist on doing defense work, vehicle brake, Horn, steering systems, lighting and other safety components such as poor are not allowed out of the car. 3, dump truck, dump truck car hop is strictly prohibited, prohibited goods mixing, loading of vehicles should not overload,stavebn tm vdce mst een. een by mlo zahrnovat analzu rizik, monost nehod charakteristik a nouzovch postup, nouzov zpracovn a obsah opaten. 4, integrovan pohotovostn plny, speciln havarijn plny a mst een by mly bt mezi sebou a s ostatnmi jednotky zapojeny v nouzi, kter jsou vzjemn propojeny. 5, havarijn pln by ml zahrnovat havarijn personl a organizace kontakt, nouzov rezervn seznam a dal informace. Informace by mly bt pravideln aktualizovny a zajist, e informace jsou pesn a platn. tyi, havarijn pln revize 1, Recenze pohotovostn plny pezkoumn formul a prvky pezkumu a opaten pijatch dvma zpsoby. Kdy host slou pedevm pro havarijn plny pro zznam v podob Recenze, prvek hodnocen pro nouzov hodnocen. . Kd pro porn ochranu konstrukce budov a nsk republice ny exploze nebezpen oblasti elektrick bezpenostnch pedpis a pedpis o porn ochranu design rafinaci ropy a chemickch podnik, napklad poadavky na pedpisech a nazench. 2. pi provdn instalace me zpsobit por, exploze, kter sti by mly bt pln nastaven peht, petlaku, micch pstroj, alarm (zvuk a svtla). 3. kde je holav plyn (pra) me unikat , holav plyn koncentrac detekce, alarm by mla bt nastavena. 4. vechny komunikoval s holav, vbun zazen s inertnm plynem, plynov penosov potrub, by mla bt nastavena zabrnit holavch a vbunch ltek do zazen, ale nemla bt samostatn zptn ventil. 5. holav plyn (pra) nastavit plamen svodi odvzduovac vvod, snadno pracovat, kde se zastavit ventily, aby pi vstupn vtrac potrub je v plamenech, peruil por plynu odvzduovac potrub ml bt nainstalovn v nejni hasicho zazen. 6. kdy dopravu holavch materil by mla odpovdat prmru potrub a stedn mrn odpor, sprvn zen prtoku, co nejvce se vyhnout statick elektiny. Antistatick opaten, jako jsou zazen, potrub, by mlo bt v souladu s technickmi pedpisy pro uzemnn design pro chemick podniky pslunch ustanoven. 7. nhl vbun petlaku nebo rychlho rozkladu vrobnch zazen nebo skladovacch zazen by mly bt vybaveny vbuchu (nevbun membrna), vvoz nonel trubice smrem k bezpenosti a aby prevence sekundrnch exploz, protiporn opaten. 8. vrobnthe principle of simplified EIA of construction projects in the region. In terms of land, linked to the implementation of urban and rural construction land increase and decrease, replacement indicators for priority areas project. Charges, into the projects of water, electricity, administrative charges and preferential policies. In the area of taxation, and settled in areas of industry and its production company, within 5 years after the completion of fiscal incentives to enterprises. In terms of financing, integration of land, tax, financial and other resources, and construct Government credit + business credit credit system, establishment of marketization, commercialization and modernization of the investment and financing platform; effective Bank-enterprise docking, encourages private capital into the Park, to raise industry development fund. 5, optimize the environment and service industries. To create policy lowlands, Highlands, integrity of service land, development land as the goal, to optimize the area under development environment. All administrative law enforcement departments to appoint a full-time personnel stationed in areas dedicated to coordinating and solving problems associated with businesses in this sector. When there are substantial issues, sector leaders arranged to personally intervene, in-person, in-person push tangible area building a green light, easy line. To further reduce and standardize administrative examination and approval items, simplify examination and approval links, improve efficiency; according to the .Since the educational practice of the mass line of the party, himself seriously in the education, practical control central eight rules and opposing the four winds and practicing three Suns, and check the spirit of Jiao Yulu, ideology, solicit opinions based on outstanding problems checked swing, careful analysis and reflection. Will now check report is as follows: first, adherence to the partys political discipline, eight in the central provision, change the style of the basic situation of 1, in compliance with the partys political disciplines. Conscientiously abide by the partys political discipline, abide by the Constitution and the rules and regulations of the party, in the political, ideological and maintain highly consistent with the CPC Central Committee on the action, there is no violation of the partys political discipline problems. 2, in the implementation of the central authorities of the eight provisions. Improving research, improving research methods, but there are less grass-roots units, primary first-hand an inadequate grasp of the problem, which is to be strengthened in the future. Second, construction, strictly in accordance with the provisions to streamline and improve the quality of meetings of the Conference. Third, streamlining file briefs, culture involves all aspects of propaganda and ideology, sometimes due to the practical needs of invention notifications, this area needs further第二单元 节能减排 -用字母表示数信息窗1 用字母表示数第一课时一教学内容：课本8-9页内容。二 教学目标：1结合具体情境，了解用字母表示数的意义和作用，学会用字母表示数。2. 初步学会根据字母所取的值求含有字母的式子的值。3. 在探究新知识的过程中，感受用字母表示数与现实生活的亲密联系，发展抽象概括能力，简历初步的代数思想。三、教学重点:学会用字母表示数及含有字母的式子的值。四、教学难点：用字母表示数，由数过渡到字母，形成由具体到抽象的认知过程。五、教学准备：ppt课件.六、教学过程：（一）口算训练（二）导入新课1、师：哪位同学能说说我们生活中还有哪些地方用到字母？ （指名回答）生1：英语课本，学校的名字下面有英文字母。生2：博习楼A座。生3：车牌号。2. 2、观看视频：某班级召开节约能源主题班会。一位男同学说：一个水龙头每分钟可节水10毫升，另一位女同学说：出门时关闭电器开关，平均每个家庭每年可节省50元电费。 问题一：你能从中找出什么问题？你能获得什么信息？生1： 一个水龙头2分钟 3分钟。节水多少毫升。生2： 每个家庭2年 3年 。能节约多少电费。生3： 我们要爱护我们的能源避免浪费。 时间 （分） 节水量（毫升） 2 210=20 3 310=30 4 410=40 . . . .我们用口来表示流水时间，那么口分钟节水量为口10如果用号来表示流水的时间，那么分钟节水量就是10在数学中，我们经常用字母来表示数。通常用字母t表示时间，t分钟的节水量表示为t10（三）新课 师：小明家原来每年的电费是m元，现在每年节省电费150元。节约用电后每年的电费是多少钱？ 生：m-1501、省略乘号，写出下面各式。（课件展示） 5 3b 8 bb 1如x3=x3=3x（数字和字母相乘省略乘号，数字在前字母在后）（四）、巩固检测2、书第9页的第一题和第二题先让学生独立完成，然后交流填写理由。3、书第10页第5题和第六题。这是结合实物图巩固用字母表示数的练习。第二组题关系比较复杂，练习时，要引导学生说清图中的意思，再用含有字母的式子表达出结果。4、书第10页第8题。这是一道联系实际巩固用字母表示数的练习。练习时，要让学生明白，大坝的高度包括两部分，一部分是水面到坝顶的高度，另一部分是水面以下大坝的高度。5、书第5页第8题。七、课堂总结：通过本节课的学习，说说你有什么收获？八、板书设计： 信息窗二用字母表示数量关系教学内容：青岛版义务教育教科书数学四年级下册P1215教学目标：1、会用字母表示常见的数量关系和计算公式，并能正确的计算。2、掌握用字母表示数的简写规则。3、感受数学语言表达的简洁性，体会数学的价值。教学重点：使学生会用字母表示常见的数量关系。教学难点：掌握用字母表示数的简写规则。教具学具： PPT课件教学过程：一、谈话激趣，引入课题：目前，节能减排，“低碳”环保以及成为了社会发展的新趋势。电动汽车作为新能源汽车，与传统汽车相比，具有清洁、节能、高效、经济等优势。我们一起来欣赏一下吧.二、探究新知：1、用含有字母的式子表示数量关系。提出问题：怎样用一个含有字母的式子表示汽车行驶速度、时间和路程之间的关系？如果t=3，电动汽车行驶了多少千米？（1）、通常用s表示路程，v表示速度，t表示时间。（2）、速度时间=路程（3）、s=vt（4）、对比两个算是，体会用含有字母表示数量关系的简洁性。（5）、如果t=3,电动汽车行驶了多少米？ 已知汽车每小时行驶60千米，即v=60,把v=60, t=3,代入数量关系，求得的s的值就是电动汽车行驶的路程。 s=vt=603=180答：电动汽车3小时行驶了180千米。（6）、归纳总结用含有字母的式子表示数量关系时，首先根据题意写出数量关系式，再用字母替换对应的量。2、用含有字母的式子表示计算公式（1）、如果用C表示周长，用S表示面积，你能用字母表示出正方形的周长和面积的计算公式吗？ 学生独立完成后小组交流 。 a 汇报展示 C=4a S=aa a 精讲点拨： 4a和a4通常可以写成4a或者4a；aa可以写成a，读作“a的平方”，表示两个a相乘。（2）你能用含有字母的式子表示长方形的周长和面积公式吗？学生独立完成 a b三、巩固练习1、一本笔记本的单价是a元。你会填写下表吗？数量（本）47101825总价（本）4a2如果用X表示工作效率，T表示工作时间，C表示工作总量。那么C=（ ），T=（ ），X=（ ）我每分钟骑v米。3.（1）5分钟骑多少米？b分钟骑多少米？(2)用v表示速度,t表示时间,s表示路程。 S=（3）如果每分钟行120m，时间是20分钟，路程是多少米？4下图是王伯伯家菜园的示意图。a米西红柿黄瓜a米b米（1）用字母表示黄瓜地的面积。当a=20时，黄瓜地的面积是多少平方米？（2）用字母表示西红柿地的面积。当a=20,b=40时，西红柿地的面积是多少平方米？（3）用字母表示王伯伯家菜地的面积。四小结这节课你有什么收获？五、板书设计用字母表示数量关系速度时间=路程 正方形的周长和面积公式s=vt C=4a S=aa 当t=3, v=60时 C=4a S=a s=vt=603 长方形的周长和面积公式=180 C=（a+b）2 答：电动汽车3小时 S=ab 行驶了180千米。用字母表示数复习课教学内容：青岛版四年级数学下册第一单元信息窗教学目标：1.通过练习进一步理解用字母表示数的意义，掌握用字母表示数的方法和含有字母的乘法算式的简写、略写的方法，体会用字母表示数的优越性。2.在具体的生活情境中，能够运用所学知识灵活的写出含有字母的式子并根据已知条件求出含有字母式子的值。3.通过拓展练习，经历“发现关系揭示规律字母表达-拓展交流”的过程，既学会知识，又体验到探究问题的方法。4.在具体事例中引导学生经历由具体到抽象的过程，培养观察、比较和抽象概括能力。教学重难点：重点:理解用字母表示数的意义，能够灵活运用所学知识表示出含有字母的式子并根据已知条件求出含有字母式子的值。难点：通过解决实际问题，经历“发现关系揭示规律字母表达-拓展交流”的过程，学会知识，体验探究问题的方法。教具、学具：多媒体课件教学过程：一、 问题回顾，再现新知。 1.同学们喜欢做游戏吗？今天，我们一起来做个游戏，好不好？小游戏： “数” 出示课件： 只， 张嘴， 只眼睛， 条腿扑通跳下水。 开始： 1 只， 1张嘴， 2 只眼睛， 4 条腿，扑通一声跳下水。 说一说游戏规则，比一比，看一看，你能说到几只。看谁说的只数多。自由说一遍后指名说一说。 讨论：（1）这个儿歌里有一个规律，你能找出来吗？ （2）小组讨论一下，将你发现的规律想办法表示出来。看谁的办法好。 （学生分组讨论，汇报讨论结果。） （3）你能用一个字母来说出任意只的儿歌吗？ 出示课件：a只，a张嘴，2a只眼睛，4a条腿，扑通一声跳下水 2.前几节课我们一起学习了“用字母表示数”，下面请同学们说一说：你学到了什么？ 学生先独立思考回忆，再小组内互相说一说。找个别学生回答，不完整的其他同学补充。预设从以下几方面展开：(1)可以用字母表示题目中的数量。(2)含有字母的式子里乘号可以记做“.”也可以省略不写。(3)根据字母的取值，可以求含有字母的式子的值。 小结知识点，摸查学生对用字母表示数的掌握情况，并引入课题。板书课题：用字母表示数练习 二、分层练习，巩固提高。 （一）基本练习，巩固新知。1.省略运算符号写出下列各式。m8 ab 15n xy xx这道题可以先让学生独立完成，再交流做法。重点让学生说出m8 为什么要写成8m 而不是m8。 xx要提示学生加号能不能省略，引导学生想到xx= x2=2x，强调在含有字母的式子里只有乘号能省略。2.出示课本第6页第9题 想一想m和n各表示什么？试着独立解释每个式子表示的意义并交流订正。（二）综合练习，应用新知。 1.开动脑筋填一填。一个正方形，每边长a米。它的周长（ ）米。一辆汽车t小时行了300千米，平均每小时行（ ）千米。李师傅每小时加工40个零件，加工了a小时，一共加工了（ ）个。 每袋面粉重a千克，每袋大米重b千克，8袋面粉和5袋大米共重（ ）千克。苏宁公司在5月5日这一天，某品牌的手机十分畅销，上午卖出75部，下午卖出100部，已知每部手机a元，这一天一共卖出（ ）元，上午比下午少卖出（ ）元。练习课一、填空： 1、学校有图书4000本，又买来a本，现在一共有（）本。2、学校有学生a人，其中男生人，女生有（）人。3、李师傅每小时生产个零件，10小时生产（）个。4、姐姐今年a岁，比妹妹年龄的2倍少2岁，妹妹今年（）岁。5、甲数是x，比乙数少，乙数是（），甲乙两数之和是（ ），两数之差是（）6、小花今年12岁，比小兰大a岁，小兰今年（）岁。7、一件上衣54元，一件裤子48元，买b套这样的衣服，要用（）元。8、一本故事书有a页，小明每天看x页，看了天，看了（）页，还剩（）页没看。9、王阿姨买了千克香蕉和千克苹果，香蕉每千克4.8元，苹果每千克5.4元，一共花了（ ）元。10、学校买来a个足球,每个m元,又买来b个排球,每个n元,一共用去( )元,足球比排球多用( )元.11、某工厂每月用水a吨,全年用水( )吨12、2a表示( )或者( )， a2表示( ) ，aaaaa( ) aaa( )13、果园里有苹果树和梨树共45棵,其中梨树有a棵,苹果树比梨树多( )棵.14、每个足球x元,买4个足球,付出200元,应找回( )元.15、三个连续自然数,已知中间一个数是m,那么前一个数是( ),后一个数是( ),三数之和是( )16、当x5时,x2( ),2x8( )。当x15时,2x24的值是( )。17、一种商品降价a元后是80元,原价是( )元.18、长方形周长计算公式用字母表示是( )19、李师傅每天做m个零件,比张师傅多做8个,两人一天共做( )个。20、每本练习本x,买了6本,付出10元,应找回( )元.21、甲数比乙数大5,如果乙数是m,那么甲数是( )。22、小红付出30元，买x本练习本，每本2元，应找回( ) 元当x10时，应找回( ) 元23、食堂买来200千克煤,已烧了a天,还剩b千克,平均每天烧了( )千克.24、一批货物a吨，第一次运走b吨，第二次运走c吨，还剩下( )吨25、食堂运来200千克煤，烧了a天，还剩下b千克，平均每天烧( )克二、省略乘号写出下面各式。 a12 a x75a 27ab2a三、判断。 1、5x5x（） 2、xxx2（） 3、a33a（）4、22（） 5、2a35a（） 6、2a3a5a（） 7、5a5a（）8、a7a8a（）四、说一说下面每个式子所表示的意义。（1）、一天中午的气温是32，下午比中午的气温降低了x。 32x表示：（2）、五（2）班有40人订阅少年文艺杂志，每本单价元。40表示：（3）、一个足球单价a元，一个篮球元。6 a4表示： （4）、张师傅每小时加工x个零件，朱师傅每小时加工15个零件。5x表示：, x15表示：。（x15）3表示：.五、求下列各式的值。1、已知a18，25求4 a2的值 2、已知x5，13求34x的值3、速生杨的树径每年大约增长3厘米。（1）如果栽种时的树径为5厘米 ，x年后这棵树的树径是多少厘米？（2）当x=6时，这棵树的树径是多少厘米？to clean and repair, it is strictly forbidden to head reaches into the mechanical stroke range. 17th article: in overhead transmission line following work should blackout, cannot blackout Shi, due isolation protection measures, crane shall not in overhead transmission line following work, through overhead transmission line should will lifting arm falls, in overhead line side work Shi, regardless of in any situation Xia, lifting arm, and rope or weights, and overhead transmission line of recently distance should not is less than Xia table provides: transmission line voltage 1000 v following 1-15 kV 20-40 kV 60-110 kV 220,000 v Allow minimum distances with the transmission line (m) vertical 1.5 level 1 1.5 2 3 4 5 6 4 6 18th: lamp voltage may not exceed 36 volts, when working in a damp place or metal containers, lamp voltage may not exceed 12 volts. 19th: pressure vessel should have a safety valve, pressure gauge, and avoid sun exposure, collisions, oxygen cylinders to prevent contaminated oil; of acetylene gas, LPG, must have a safety device to prevent tempering. 20th: x-ray and gamma-ray flaw detector operation area, non-operator, not allowed to enter. Article 21st: corrosion, dust and radioactive and toxic work, protective measures are required, and to carry out regular inspection. Spider-man 22nd section III: Spider-man to regular medical examinations of the medical diagnosis, who suffer from high blood pressure, heart disease, anemia, epilepsy and other discomfort in the Spider-man shall not engage in aerial work. 23rd: Spider-man dressed spirit, banned the wearing of hard bottom and easy slip-on shoe nail. 24th: Spider-man material stack stationary, tools should turn into a tool bag, transfer prohibited throwing of objects. 25th: in case of bad weather (such as wind in the above grade) construction safety, prohibition of the open air, lifting and piling. 26th article: ladder shall not deficiency document, no padded using, ladder cross document spacing to 30 cm suitable, using Shi top to tied prison, bottom should take anti-sliding measures, single ladder and ground angle to 60 degrees suitable, ban II people while in ladder Shang job, as needed received long using, should lashing firm, people Word ladder in end of feet pulled prison, in channel at using ladder, due guardianship or set fence. 27th: no security measures, prohibited in hip joints, supports, trusses of the roof truss cantilever beams, and choose the frame and half fixed widget or job to walk on, Spider-man and the ground . Nine, ten basic security to prevent vehicle damage claim 1, without legal training of qualified certified personnel not familiar with vehicle performance is not driving a car. 2, should insist on doing defense work, vehicle brake, Horn, steering systems, lighting and other safety components such as poor are not allowed out of the car. 3, dump truck, dump truck car hop is strictly prohibited, prohibited goods mixing, loading of vehicles should not overload,ch zazen, budov a konstrukc, tanky a jin zsuvky prmyslov vody, krom ustanoven vodu tak, by mlo bt instalovno v oblasti s vodou k utsnn vrtu, uzavrac ventil, aby se z