时间状语从句十道题 急用(本人这方面极差，希望能帮忙解释一下为什么这么填，赏分)

我11岁了，用英语说是， I"m 11 years old.

Robby was 10 for his first piano lesson in my class.robby在10岁的时候第一次上我的钢琴课。

be11-yearoldboy=is/was11-yearoldboy是十一岁大之男孩。e.g.Heis11-yearoldboynow.他现在是个十一岁大之男孩。an11-year-oldboy一个十一岁大之男孩。e.g.An11-year-oldboycannotdothiscalculusyet.一个十一岁大的男孩还未能做微积分.

在英语中，表示年龄的词语组是“years old”，意思为“……岁”。而在写法上，有些地方需要注意一下的，即years old 和year-old因为years old表达的是“某人多少岁了”，而year-old则表示“多少岁的人”。所以，这就是years old和year-old的区别

艺人名称：City High唱片名称：《City High》出版公司：环球唱片 发行日期： 2001-9 曲目列表：1. Didn‘t Ya2. Three Way3. Why4. Song For You5. 15 Will Get You 206. Cat And Dogs7. Caramel8. Best Friends9. Sista10. What Would You Do11. So Many Things12. The Only One I Trust13. City High Anthem14. You Don‘t Know Me歌词 [Robby (Ryan)](What"s up my nigga?)Heh, chillin" yo(What"s up man, ya ready to go? Come on!)Naw yo, you just go ahead(What"s wrong with you man?)(Wifey got you buggin" again)Pshh, I just don"t understand, ya know(Understand what man? Huh?)She ain"t talkin" to me son(Word)Yo I need you to do me a favor yo(What?)You gotta call her homie(What"chu want me to call her for)You gotta tell her for me(Tell her what man)That I love her so strongly(Why don"t you just tell her yourself)Cause she won"t listen to me now(Damn)Without love in my heartI might as well be dead(Hold up, hold up, you ain"t gonna be killin" yourself nigga)So can you help me out?(I"m callin i"m callin)You"re the only one who cares[Ryan (Claudette)]Yo shortyI just got off the phone with RobbieHe told me to come talk to you(Yeah, bout what?)He said y"all having problemsAnd you left him, now he"s all confused(Man, so what?)Now girl why you buggin?You know you was made for himAnd him for youI ain"t trying to butt inI just wanna be a friendAnd he asked me to call you[1] - You gotta call her homieAnd tell her for meThat I love her stronglyShe won"t listen to meWithout love in my heartI might as well be deadPlease help me nowYou"re the only who caresYou gotta call her homieAnd tell her for meThat I"m really sorryShe won"t listen to meWithout love in my heartI might as well be deadPlease help me nowYou"re the only who cares[Ryan]Hmm, girl this thing has gone on, long enoughCan"t you seeHe don"t know the true reason that you left himBaby is cause of me, whoaHe would be real surprisedTo find that I"m the new apple of your eyeWhat kind of friend am I?To take advantage of - my best friend"s trust[Repeat 1][Claudette (Robby)]If you wanna knowWhy I did - what I did(Tell me why did you do it)I got tired of being aloneWhile you was out trickin"(Who told you I was trickin?)I guess female dogs can"t learn tricks tooYou see I"m not the bitch, baby payback isAnd what you did came back to you, oh

这里的11-year-old表示11岁的，当作形容词使用的。one 11-year-old boy 一个11岁的男孩。或者说The boy is 11 years old. 这个男孩11岁。

eleven years old

6-year-old放在名词前，做定语6 years old 放在系动词后，作表语

12year old

小题1:(He was) 11 years old./ He was 11.小题2:(He was) A piano teacher. 小题3:He felt surprised./ Surprised.小题4:(He said that) The strict finger positioning would rob some kids of fun of playing.小题5:It (His way) was good/ wonderful/ successful/ effective./ It was a proper way/ … 小题1:从第一段的句子：As an eleven-year-old boy, he became the youngest pianist ever to perform a concert at the theater. 可知答案是：(He was) 11 years old./ He was 11.小题2:从第二段的句子：His father Zhang was a piano teacher. 可知牛牛的爸爸是个钢琴老师：(He was) A piano teacher. 小题3:从第三段的句子：To my surprise, he played nearly 80 percent correct,”可知牛牛的爸爸感到很惊讶。He felt surprised./ Surprised.小题4:从第四段的句子：He said that the strict finger positioning would rob some kids of fun of playing.可知严格的手指位置会让孩子没有谈钢琴的乐趣： (He said that) The strict finger positioning would rob some kids of fun of playing.小题5:这题答案可以学生自己发挥：It (His way) was good/ wonderful/ successful/ effective./ It was a proper way/ …

Jean Todt (born February 25, 1946) is a former executive director of Scuderia Ferrari, the Ferrari company"s Formula One constructor. On October 25, 2006, he was appointed as the company"s CEO. On March 18, 2008, Todt resigned as CEO and assumed a "special appointment" within the company"s racing department. He resigned this position one year later.On 23 October, 2009, he was elected as president of the FIA, motor sport"s world governing body. Todt, who succeeds Max Mosley, stood against Finland"s former world rally champion Ari Vatanen for the position.1.Life and careerTodt was born in the commune of Pierrefort in the Cantal department of France. His father was Polish Jew who escaped to France during World War II. His mother was French. Todt"s motorsport career began when he borrowed his father"s Mini Cooper S for a friend to drive in a rally. Todt soon became a rally driver himself. He moved to various driving roles in rally series, but decided his strength was as a co-driver; he continued as such with the Peugeot Talbot Sport rally team until his retirement from competition in 1981.2.Peugeot Talbot SportThe team moved Todt into a management-oriented position, charging him to organize the design and construction of the 205 Turbo 16 for the 1984 World Rally Championship season. After a slow start, the 205 won the world title in 1985 and 1986; other Todt-managed models continued to dominate, winning rally championships, hill climbs, and with the highly successful Peugeot 905, the Le Mans 24 hours and the World Sportscar Championship, into the 1990s. Peugeot, despite Todt"s continual urging, refused to enter the Formula One Championship, and when a position opened at the Ferrari F1 team, Todt took the opportunity in 1993.3.Scuderia FerrariJean Todt at Spanish GP 2001Todt was the first senior appointment of Ferrari president Luca di Montezemolo who had been placed in charge of a once legendary team which "had become something of a joke."The Todt/Montezemolo leadership hired Michael Schumacher in 1996, with whom came strategist Ross Brawn, and designer Rory Byrne. The Independent credited Todt with melding this combination "into a cohesive structure devoid of the polemics which were so rife."The fortunate combination produced a nearly-unbeatable team. Todt and Ferrari president Luca di Montezemolo have since been considered responsible for turning Ferrari from a has-been team, helpless without founder Enzo Ferrari, into the powerhouse it is today.Following much speculation as to FIA President Max Mosley"s impending retirement, rumors arose in 2004 to the effect that Todt would run for the office. Mosley commented that though Todt would make an excellent president, he was quite happy at Ferrari; however, it had long been assumed that when Michael Schumacher retired from F1, Todt would leave his job. In an apparent bid to maintain Todt"s loyalty, Ferrari president Luca di Montezemolo promoted Todt to the head of the entire Ferrari operation, including street car production.He remained as the Team Principal of the Scuderia F1 Team for one more season, and was replaced by Stefano Domenicali on 1 January 2008, however he still remained as CEO of Ferrari. On March 17, 2009, it was announced that Todt had resigned, leaving Ferrari completely.The French government has made Todt a Chevalier of its Legion d"Honneur. He was further honoured with the Grand Officier rank of the honour in January 2007.Also, in July 2006, Todt was given the official Malaysian royal title of "Datuk" by Sultan of Terengganu, which is the Malaysian equivalent of a British knighthood - he is now widely addressed in Malaysian media as Datuk Seri Jean Todt.4.FIA PresidencyAs of October 23, 2009, Jean Todt was elected president of the FIA, with 135 votes against 49 votes for ex-driver Ari Vatanen.5.Personal lifeOn September 28, 2005, Todt"s engagement to actress Michelle Yeoh was reported.Yeoh has subsequently denied the engagement. As recently as March 2007, Yeoh denied assertions as to an upcoming marriage. On July 31, 2008, Ms. Yeoh confirmed the rumor that she was engaged (to Jean Todt) during an interview with Craig Ferguson on CBS"s The Late Late Show.Todt joined the Malaysia My Second Home Programme(MM2H) in April 2009. On 13 May 2009, Jean Todt was named as the Tourism Malaysia"s Ambassador.Todt has a small role in the film Astérix at the Olympic Games.Todt"s son Nicolas is a manager of Formula One drivers including Ferrari incumbent Felipe Massa.

英语十岁是什么？

他9岁。（1）He"s nine years old. (2) He"s nine-year old.

【答案】【小题1】B【小题2】C【小题3】A【小题4】B【小题5】A【答案解析】试题分析：这篇文章讲的是11岁的男孩Hamad和他的绘画天赋，他将在这个周末在Llangollen"sGardeningShow举行第一次画展。【小题1】主旨题：从第一段的句子：An11-year-oldboywhohasbeencomparedtoSpanishImpressionist(印象派画家),thegreatPabloPicasso,可知这篇文章讲的是Hamad和他的绘画天赋，选B【小题2】细节题：从文章第三段的句子：Buthebegantopainthisfavouritefootballplayer,CristianoRonaldo,usingPicasso"strademarks(标志)—brightcoloursandimpressionisticforms.可知Hamad非常喜欢CristianoRonaldo，选C【小题3】细节题：从文章第三段的句子：Buthebegantopainthisfavouritefootballplayer,CristianoRonaldo,usingPicasso"strademarks(标志)—brightcoloursandimpressionisticforms.可知Hamad画的第一副CristianoRonaldo的画有明亮的色彩和印象派的形式，选A【小题4】猜词题：从第五段的句子：Theylikedthemverymuchandeveryonewaseagertobuy,sothefirstsixpaintingshavebeensnappedup.可知"snappedup"的意思是“很快销售”，选B【小题5】细节题：从文章第五段的句子：HehadtalentandIthoughtPicassohadbeenreborn."可知SteveTurner高度评价Hamad，选A考点：考查新闻报道类短文

我讨厌

1. Many experts think pigs are ______ to train than dogs or cats.A. easier B. much easy C. more easily D. too easy2. Ginger can"t dance as ______ as Jasmine, but she still got the prize.A. beautifully B. more beautifully C. less beautifully D. the most beautifully3. Matt became so ______ when I dropped the coffee on her shirt, which made me quite upset.A. forgetful B. carefully C. angry 　D. sadly4. Often life is much ________ outside the big cities, as is true in other countries as well.A. slow B. slower C. slowest D. the slowest5. Mary looked _____ because she lost her new watch last week.A. friendly B. upset C. happy D. excited6. Mr Wang is usually the first one to come to work, but today Xiao Li came than he.A. early B. earliest C. earlier D. very early7. The beef tastes the pork. Please make yourself at home.A. as better as B. much better than C. the best than D. as well as8. I need _____ bananas to make fruit salad. Could you please buy some? A. few B. a few C. little D. a little9. The more you smile, the _______ will feel in your everyday life. A. happy B. happier C. happiest D. the happiest10. He has read many books on history, so it"s _______ for him to answer these questions.A. hard B. impossible C. serious D. easy11. When he heard a cry for help, he can run out as______ as he could.A. hardly B. finally C. quickly D. slowly12. If you save every day, you"ll be able to buy a mobile in a year.A. a little B. little C. a few D. few13. The black suitcase is the red one. I"ll take the red one.A. so expensive as B. much expensive than C. more expensive as D. much more expensive than14. The boy checked his test paper in order to get full marks.A. enough careful B. enough carefully C. careful enough D. carefully enough15. We feel so that China has sent its first space laboratory, Tiangong-1 into orbit successfully.A. exciting B. excited C. excite D. excitedly16Take a look at this photo. It"s the ________one I have ever taken.A.beautiful B. uglier C. more expensive D. prettiest17. The fish soup tasted so that the guests asked for more.A. bad B. terrible C. well D. good18. Mobile phones are very popular nowadays and they are_______ than before.A. cheap B. cheaper C. cheapest D. the cheapest19. It"s difficult to live in a foreign country，________if you don"t speak the languageA. importantly B. naturally C. especially D. usually20. The house price in Shanghai is __________ to become lower and lower in the coming years.A. politely B. possibly C. likely D. happily21. With the help of computers, writing does not seem so _________ as it used to be.A. difficult B. less difficult C. more difficult D. the most difficult 22. Do you think which means of transport is , the underground or the plane?A. safe B. safety C. safest D. the safest23. The roast beef tastes so . May I have one more piece, mum?A. well B. bad C. delicious D. terrible24. Among the earrings I choose pair because I didn"t bring enough money that day.A. cheap B. cheaper C. cheapest D. the cheapest25. Alice"s mother bought Alice a new dress. This beautiful dress made her look .A. quietly B. lovely C. politely D. gently26. My son likes reading stories. Now he can tell a story as as his sister.A. better B. best C. good D. well27. The film Tintin "s Adventure is , so it is welcomed by teenagers.A. amazing B. excited C. boring D. bored28. It"s said that the road we drove along just now is ________ in this area.A. busy B. busier C. busiest D. the busiest29. The film The Flowers of War is as as the one we saw last weekA. attractive B. more attractive C. most attractive D. the most attractive30. As soon as George heard the bad news, his face turned .A. red B. pale C. sadly D. happily31. Jenny likes the new neighborhood because people here are .A. friendly B. softly C. politely D. nicely32. Do you know of all the words we used in 2011 "hold" became in China?A. hot B. hotter C. hottest D. the hottest33. Tea is _____ drink in the world besides water.A. popular B. more popular C. most popular D. the most popular34. Steven completed the science test______ in our class yesterday.A. most quickly B. more quickly C. less quickly D. quickly35. The actress is at least 50, but she looks _______than she really is.A. very young B. much younger C. very old D. much older 36. Nowadays science fiction isn"t as ____________ as cartoons among teenagers. A. popular B. more popular C. less popular D. the most popular37. We are glad to see that Shanghai is developing _______ these years than ever before. A. quickly B. less quickly C. more quickly D. the most quickly38. The cheese cake tasted so ______ that the kids asked for more.A. delicious B. well C. bad D. badly39. —Why didn"t you enjoy the talk? —It was ________talk that I had ever listened to. A. the most interesting B. the least interesting C. more interesting D. 1ess interesting40. Guo Yue did quite _______ at the World Table Tennis Championship（锦标赛），but Zhang Yining did even ________.A. better; well B. well; well C. well; better D. better; better41. — Whose picture is better, Jack"s or Tom"s?— Both of them are good. I think Jack draws Tom. A. as good as B. as well as C. better than D. worse than42. It gets very here in summer. A. cool B. cold C. warm D. hot43. Be ________, and you will do well in the English exam.A. careful B. polite C. sure D. friendly44. Lin Tao is good at all the subjects at school, _________English.A. really B. mostly C. especially D. exactly45. —The coat is too expensive. —Look, here"s another one. It"s________ and nicer. 结：

HNO3

你首先要明白权是什么意思。字义上讲，权就是秤砣，他是用来横来物体重量的。所以，某数权越高，他占得比重就越大，越影响结果。比如某学期你期中考试80分，期末考了90分，那么你两次考试的算术平均分就是85分。但是我们觉得期末考试比较重要，他应该占平均分的60%，期中考试占40%，那么两次考试的加权平均数就是80*40%+90*60%=86，比算数平均大，因为权重大的分数高，如果期中考试占40%而期末占60%那么加权平均就是80*60%+90*40%=84，比算数平均小。其实算术平均数就是认为每个数占得权重一样大，比如上面的例子就是期中考试跟期末考试一样重要各占50%，80*50%+90*50%=85。所以加权平均跟算数平均究竟哪个大，主要是看高于平均数的大数占得权重大小（是否高于50%）

权数相等条件下，简单算术平均数和加权算术平均数计算结果相同

铵铵氨分子衍生出的阳离子了解铵的更多含义了解铵的更多含义中国科协权威合作机构中国科协主办科普信息化平台性质还原性结构用途检验方法铵是一种阳离子，化学式：NHu2084。是由氨分子衍生出的阳离子。氨分子与一个氢离子配位结合就形成铵离子。由于化学性质类似于金属离子，故命名为“铵”。基本信息中文名 铵外文名 Ammonium质量 18.03851所属学科 化学性质由氨衍生的一种离子NHu2084或基“―NHu2084”。也叫“铵根”，它是化学中的一种阳性复根，用NHu2084表示。它和一价金属离子相似。它的盐类称为铵盐。如化肥硫铵和碳酸铵的分子都含有铵。铵离子的性质和钾离子相近，在溶液中呈+1价。铵盐都呈白色晶体，加碱研磨（相当于加热）能生成有刺激性气味的氨气（化学式：NHu2083），铵盐受热会分解。还原性铵根离子有较强的还原性，其中的负三价的氮化合价上升的趋势较强，会被强氧化剂氧化成N2，氮氧化物甚至NO3。相关反应式：与溴反应：3Br2+2NH4=3Br+N2↑+8H与双氧水反应：3H2O2+2NH4=N2↑+2H+6H2O与氯气反应：3Cl2+2NH4=3Br+N2↑+8H与亚硝酸反应：5HNO2+NH4=6NO↑+4H2O+H硝酸铵爆炸：NO3+NH4=（加热或撞击）=N2O↑+2H2O与浓硝酸反应：7NO3+6H+NH4=8NO2↑+5H2O与稀硝酸反应：5NO3+3NH4+2H=8NO↑+7H2O与氧气反应：第一步5O2+4NH4=（加热，Pt催化剂）=4NO↑+6H2O+4H第二步：4NO+3O2+2H2O=4NO3+4H总反应：2O2+NH4=（加热，Pt催化剂）=NO3+H2O+2H与次氯酸钠反应：4ClO+NH4=4Cl+NO3+H2O+2H与重铬酸反应：（1）稀：Cr2O7+2NH4+6H=2Cr+N2↑+7H2O（2）中：7Cr2O7+6NH4+50H=14Cr+6NO2↑+37H2O（3）浓：4Cr2O7+3NH4+26H=8Cr+3NO3+19H2O与高锰酸反应：（1）稀：8MnO4+5NH4+14H=8Mn+5NO3+17H2O（2）浓：8MnO4+3NH4+2H=8MnO2↓+3NO3+7H2O结构铵离子是正四面体型的

加权算术平均数在什么条件下等于简单算术平均数 1、加权权重都是一样时 2、各项的数值都是一样时

NH4NO3是硝酸铵的化学分子式

2012版初二上册数学有 是第六章

（1）由图可知，半导体电阻R与定值电阻R0串联，当环境温度升高时，半导体电阻会越来越小，根据欧姆定律可知，电路中的电流越来越大，应该给电路中串联一个定值电阻，这样就可以防止电路中的电流过大而烧坏仪表；（2）由图象可知，环境温度为20℃时半导体电阻的阻值R=50Ω，因串联电路中总电阻等于各分电阻之和，所以，由I=UR可得，电源的电压：U=I（R+R0）=0.2A×（50Ω+10Ω）=12V．故答案为：保护电路；50；12．

如：A:B:C:D=1:2:3:9加权平均数：(Ax1+Bx2+Cx3+Dx9)/(1+2+3+9)如果比值相加刚好等于10就更容易了......

铵根的化学式是NH4+。氨气的化学式是NH3。铵盐是一类物质，没有化学式。硝酸铵的化学式是NH4NO3。

硝酸铵化学公式为NH4NO3。硝酸铵是一种铵盐，呈无色无臭的透明晶体或白色晶体，极易溶于水，易吸湿结块，溶解时吸收大量热，受猛烈撞击或受热爆炸性分解，遇碱分解。是氧化剂，用于化肥和化工原料。纯硝酸铵在常温下是稳定的，对打击、碰撞或摩擦均不敏感。但在高温、高压和有可被氧化的物质（还原剂）存在及电火花下会发生爆炸。硝酸铵主要用作肥料及工业用和军用炸药，并可用于杀虫剂、冷冻剂、氧化氮吸收剂，制造笑气、烟火等。

算术平均数（ arithmetic mean），又称均值，是统计学中最基本、最常用的一种平均指标，分为简单算术平均数、加权算术平均数。它主要适用于数值型数据，不适用于品质数据。根据表现形式的不同，算术平均数有不同的计算形式和计算公式。算术平均数是加权平均数的一种特殊形式（特殊在各项的权重相等）。在实际问题中，当各项权重不相等时，计算平均数时就要采用加权平均数；当各项权相等时，计算平均数就要采用算术平均数。

（1）由图象可知，温度为20℃时，半导体电阻阻值R=50Ω；（2）∵串联电路中总电阻等于各分电阻之和，∴由欧姆定律可得，电源的电压：U=I（R+R0）=0.2A×（50Ω+10Ω）=12V；（3）当电流表的示数I′=0.4A时，电路总电阻：R总=UI′=12V0.4A=30Ω，半导体电阻的阻值：R′=R总-R0=30Ω-10Ω=20Ω，由R-t图象知，半导体电阻为20Ω时，环境温度是40℃，半导体电阻的电功率：PR=I′2R′=（0.4A）2×20Ω=3.2W．答：（1）当环境温度为20℃时，半导体的电阻是50Ω；（2）电源的电压为12V；（3）电流表的读数为0.4A时，当时环境温度为40℃，半导体电阻的电功率是3.2W．

【答案】导体；零【答案解析】试题分析：半导体的导电能力介于导体和绝缘体之间，常见的半导体有硅和锗，还有些物体在温度降到足够低时电阻变为零，这是超导现象。考点：半导体、超导

导电性能介于导体与绝缘体之间的叫半导体．半导体材料制成的二极管具有单向导电性． 故答案为：导体；绝缘体；单向导电．

硝酸化学式：HNO3，硝酸具有强氧化性、腐蚀性的强酸，属于一元无机强酸，是六大无机强酸之一，也是一种重要的化工原料，其水溶液俗称硝镪水或氨氮水。在工业上可用于制化肥、农药、炸药、染料、盐类等；在有机化学中，浓硝酸与浓硫酸的混合液是重要的硝化试剂迹卖让。所属的危险符号是O（Oxidizing agent 氧化剂）与C（Corrosive 腐蚀品） 。扩展资料硝酸分子中氮元素为最高价态（+5）因此硝酸具有强氧化性，其还原产物因硝酸浓度的不同而有变化。从总体上说，硝酸浓度越高，平均每分子硝酸得到的电子数越少，浓硝酸的还原产配搜物主要为二氧化氮，稀硝酸主要为一氧化氮，更稀的硝酸可以被还原为一氧化姿局二氮、氮气、硝酸铵等，需要指出的是，上述只是优势产物，实际上随着反应的进行，硝酸浓度逐渐降低，所有还原产物都可能出现。

加权平均值即将各数值乘以相应的权数，然后加总求和得到总体值，再除以总的单位数。举例： 下面是一个同学的某一科的考试成绩： 平时测验 80， 期中 90， 期末 95 学校规定的科目成绩的计算方式是： 平时测验占 20% 期中成绩占 30% 期末成绩占 50% 这里，每个成绩所占的比重叫做权重。那么， 加权平均值 =( 80*20% + 90*30% + 95*50% )/(20%+30%+50%）=90.5 权调和平均数 适用于分组资料的计算，其计算公式为： 平均数=（M1+M2+…+Mn）/(M1/X1+M2/X2+…+Mn/Xn)=∑Mi/∑(Mi/Xi) 具体计算方法如下： （1）先计算出各个变量值的倒数，即1/X； （2）计算上述各个变量值倒数的算术平均数，即[∑(1/X)]/n; （3）再计算这种算术平均数的倒数，即n/[∑(1/X)]，就是调和平均数。

硝酸铵化学式为NH4NO3，铵根离子中氮元素的化合价为-3，硝酸根离子中氮元素化合价为+5。

加权算术平均数和加权调和平均数的区别和联系加权算术平均数一般用在未知分子的情况下,即总体标志总量未知.调和算术平均数一般用在未知分母的情况下,即总体单位数未知

1、硝酸铵溶于水的化学方程式：NH4NO3+H2O=(可逆)NH3.H2O+HN03。 2、硝酸铵（NH4NO3）是一种铵盐，呈无色无臭的透明晶体或呈白色的晶体，极易溶于水，易吸湿结块，溶解时吸收大量热。受猛烈撞击或受热爆炸性分解，遇碱分解。是氧化剂，用于化肥和化工原料。

NH4NO3

nh4no3

【答案】：C大小的因素有两个：①各组标志值的大小；②权数的影响。权数对算术平均数的影响，不取决于权数本身数值的大小，而是取决于作为权数的各组次数占总体次数的比重的大小。各组次数占总体次数的比重是计算加权算术平均数的实质权数。

是两个不同的颗粒呀：NH4+ NO3-

NH4NO3和NH4CI

简单算术平均数是在一组数据中所有数据之和除以数据的个数，如将各个地块的小麦产量直接相加得到总产量，再除以总亩数，得到平均亩产量。加权算术平均数是将变量乘权数求出标志总量，把权数相加求出总体总量，然后用前者除以后者，它适用于对分组的统计资料计算平均数。如将各个地块的产量按不同产量水平分成若干组，先将各组产量乘以各组的地块数求出各组的总产量后，相加求得全部地块的总产量，再除以地块总数，这样计算的平均亩产量称为加权算术平均数。算术平均数的优点是利用了所有数据的特征。但它也有不足之处，正是因为它利用了所有数据的信息，容易受极端数据的影响。扩展资料注意事项：在使用平均指标时，既要关注总量平均数，也应关注分类指标平均数，这样有助于我们正确使用平均数，从而进行比较分析。例如在使用居民消费价格指数（CPI）时，既要运用CPI总指数，也要综合使用食品、衣着等大类指标，有时候还要使用粮食、肉禽等具体小类商品的指数。

作用是被评价对象的不同侧面的重要程度的定量分配。在计算加权平均数时，常用权数来反映对应的数据的重要程度：权数越大的数据越重要。1、权的意义权有两种意义：①数据出现的个数；②数据所占的百分比。权数越大的数据在总体中所占的比例越大，它对加权平均数的影响也越大。2、权的定义“权”指的是一个比例和所占分数，加权平均值即将各数值乘以相应的权数，然后加总求和得到总体值，再除以总的单位数。加权平均值的大小不仅取决于总体中各单位的数值（变量值）的大小，而且取决于各数值出现的次数（频数）。由于各数值出现的次数对其在平均数中的影响起着权衡轻重的作用，因此叫做权数。因为加权平均值是根据权数的不同进行的平均数的计算，所以又叫加权平均数。扩展资料1、在日常生活中，人们常常把“权数”理解为事物所占的“权重”。比如现在有一年级学生一个，两年级学生一个，三年级学生两个，我们就说一年级学生权是1/4，三年级学生权是2/4。某一指标的权重是指该指标在整体评价中的相对重要程度。加权平均数是不同比重数据的平均数，加权平均数就是把原始数据按照合理的比例来计算。若 n个数中，x1出现f1次，x2出现f2次，…，xk出现fk次，那么(x1f1 + x2f2 + ... xkfk)/（f1 + f2 + ... + fk） 叫做x1，x2，…，xk的加权平均数。f1，f2，…，fk是x1，x2，…，xk的权.。2、加权平均数与算术平均数加权平均数与算术平均数类似，不同点在于，数据中的每个点对于平均数的贡献并不是相等的，有些点要比其他的点更加重要。加权平均数的概念在描述统计学中具有重要的意义。

A、由硝酸铵的化学式为（NH4NO3）可以看出，它每个分子含有2个氮原子、4个氢原子、3个氧原子，共9个原子，故A错误；B、根据硝酸铵的化学式可知，硝酸铵的相对分子质量=14×2+4+16×3=80，故B错误；C、根据硝酸铵的化学式（NH4NO3）可知，其中氮、氢、氧三种元素的质量比═（14×2）：（1×4）：（16×3）=7：1：12，故C错误；D、硝酸铵中N元素的质量分数为=14×280×100%=35%，故D正确．故选D．

加权平均值即将各数值乘以相应的权数，然后加总求和得到总体值，再除以总的单位数。举例：下面是一个同学的某一科的考试成绩：平时测验 80， 期中 90， 期末 95学校规定的科目成绩的计算方式是：平时测验占 20%期中成绩占 30%期末成绩占 50%这里，每个成绩所占的比重叫做权重。那么，加权平均值 =( 80*20% + 90*30% + 95*50% )/(20%+30%+50%）=90.5权调和平均数适用于分组资料的计算，其计算公式为：平均数=（M1+M2+…+Mn）/(M1/X1+M2/X2+…+Mn/Xn)=∑Mi/∑(Mi/Xi)具体计算方法如下：（1）先计算出各个变量值的倒数，即1/X；（2）计算上述各个变量值倒数的算术平均数，即[∑(1/X)]/n;（3）再计算这种算术平均数的倒数，即n/[∑(1/X)]，就是调和平均数。

硝酸根的化学式为：NOu2083u207b。硝酸根是指硝酸盐的阴离子，化学式为NOu2083u207b，硝酸根为－1价，其中N为最高价＋5价。用途硝酸银实验室中用于检验氯离子，因为银离子和氯离子能结合成不溶于酸的白色沉淀氯化银。一般还与稀硝酸配合用于检验。在有机化学中，硝酸根可以用于生成硝酸酯（RONO2），比如卤代烃与硝酸银反应就可以生成卤化银沉淀和硝酸酯。硝酸钠常见的化肥。硝酸铵（NHu2084NOu2083）简称硝铵，常见的化肥。硝酸钾常见的复合肥料。

（1）根据相对分子的质量（式量）为组成分子的各原子的相对原子质量之和，可得硝酸铵的相对分子质量为14×2+4+16×3=80．（2）根据化合物中各元素质量比=各元素的相对原子质量×原子个数之比，可得硝酸铵中氮、氢、氧元素的质量比为（14×2）：（1×4）：（16×3）=7：1：12．（3）NH4NO3中氮元素的质量分数为：14×280×100%=35%．（4）100千克硝酸铵中含氮元素：100kg×35%=35kg；（5）含35kg氮元素需要碳酸氢铵的质量为：35kg÷1414+1×5+12+16×3×100%=197.5kg；（6）该袋化肥中氮元素的质量分数为：90%×35%=31.5%．故答案为：（1）80；（2）7：1：12；（3）35%；（4）35；（5）197.5；（6）31.5%．

1. 绝对权数平均：（1000*12%+2000*10%+1500*7%+2800*10.5%）÷7300=9.85%2. 相对权数平均：（12%+10%+7%+10.5%）÷4=9.875%扩展资料：Yi代表不同时期的观测值(i=1，2，…，n)；n代表总体中的数据点数；Wi代表各个观察值对应的权数，Wi在0到1之间，即0≤Wi≤1。加权算术平均法是算术平均法的一般形式，即权数都相同时亦可用此公式形式。但权数都相同时。还是用简单算术平均法进行计算更简捷。参考资料来源：百度百科-加权算术平均法

硝酸铵的化学式怎么写？硝酸铵的化学式为NH4NO3。