twinkle100
高中语法的难度加大,在考试中的比例也大大增加了,完型、阅读、写作都需要语法的熟练运用。今天老师为大家整理了语法中数词的用法,赶紧学起来哦!基数词表示数目多少或顺序先后的词叫数词。1.基数词的构成:1-10 one, two, three, four, five, six, seven, eight, nine, ten;11-19 eleven, twelve, thirteen, fourteen, fifteen, sixteen,seventeen, eighteen, nineteen;20-90 twenty, thirty, forty, fifty, sixty, seventy, eighty, ninety;≥ 100100 a/one hundred;1,000 a/one thousand;1,000,000 a/one million;1, 000,000,000 a/one billion = a/one thousand million2. 基数词的用法1)作主语:Three will be enough for us.三个对我们来说就足够了。Two of the girls are from Tokyo.这些姑娘中有两位来自东京。2)作宾语:Four people applied for this job, but we only need one.四个人申请这工作,但我们仅需一人。3)作表语:The population of China is over 1.3 billion.中国有十三亿多人口。I’m twenty while my brother is sixteen.我二十岁,我弟弟十六岁。4)作定语:We have 300 workers in our company.我们公司有三百名员工。Forty students were involved in the interview. 四十名学生参加了这次采访。5)作同位语:You two clean these seats.你们两个打扫这些位子。Have you got tickets for us three?有我们三个人的票吗?序数词表示顺序或等级。1. 序数词的构成:1-10:first 1st; second 2nd; third 3rd; fourth 4th; fifth 5th; sixth 6th; seventh 7th;eighth 8th; ninth 9th; tenth 10th;11-19:eleventh 11th; twelfth 12th; thirteenth 13th; fourteenth 14th ;fifteenth 15th; sixteenth 16th; seventeenth 17th; eighteenth 18th;nineteenth 19th;20-90:twentieth 20th; thirtieth 30th; fortieth 40th; fiftieth 50th; sixtieth 60th;seventieth 70th; eightieth 80th; ninetieth 90th;≥100:100 hundredth;1,000 thousandth;1,000,000 millionth;1,000,000,000 billionth2、序数词的用法1)作主语:The second is what I really need.第二个是我真正需要的。The first bottle has been full but the second is empty.第一个瓶已满,但第二个还空着。2)作宾语:I got a third in biology.我生物得到了第三名。Do you prefer the first or the second?第一个和第二个你更喜欢哪一个呢?3)作表语:I will be the first to support you and the last to oppose you.我将是第一个支持你的人,也是最不会反对你的人。Columbus was the first who discovered America.哥伦布是第一个发现美洲的人。4)作定语:I’ll try a second time and see if I can do it.我还要试一次,看看我能否做得了。Take the first turn to the right and then the second turn to the left and you’ll get there.在第一个转弯处向右转,然后在第二个转弯处向左转就到了。5)作状语:He came second in the race.他在赛跑中得了第二名。It was a snowy day when we first met.我们初次见面时是一个下雪的日子。3、 序数词前冠词的使用1) 明确指明了先后顺序或一系列事物按一定的规律排列时,序数词前用定冠词。This is the second time that I have been in London.这是我第二次来伦敦。Alva is the fifth child of the Whites.阿尔瓦市怀特家的第五个孩子。2) 表示“又一、再一”,不强调顺序时,序数词前用不定冠词。You have bought four toys today. Why do you want to buy a fifth one?今天你已经买了四个玩具了,为什么还想再买一个呢?I failed again, but I will try a third time.我又失败了,可是我要再试一次。3) 序数词前有形容词性物主代词、名词所有格或其他修饰语时不用任何冠词。My first five years of childhood was spent with my grandparents.我五岁前是和祖父母一块度过的。Mrs. Black’s second child is a genius.布莱克夫人的第二个孩子是个天才。4) 序数词与名词构成复合形容词时,冠词由被修饰词而定。此时序数词是复合形容词的一部分而不是独立的,前面的冠词完全由这个形容词所修饰的名词而定。This MPV car is a second-hand one.这辆商务车是二手的。Habit is second nature.习惯是第二天性。5) 序数词还可作副词,此时不用任何冠词。First I am short of money; second I haven’t enough time.首先我缺钱,其次我没有足够的时间。6) 序数词用在表示“每隔……”的every 后,其前不用冠词。every second day 每隔一天every fifth day 每隔四天every second line 每隔一行7) 某些固定搭配中序数词前不用冠词。first of all 首先at first 起初at first sight 乍一看,第一数词的用法1. 分数:表示分数时,分子须用基数词,分母须用序数词。(分子是1以上的任何数时,作分母的序数词要用复数形式。)1) 真分数通常用英语单词表达。one-fourth 四分之一two-fifths 五分之二a quarter 四分之一2) 分子和分母的数目较大时,两者都用基数词,之间用over/by/out of/in 连接。Seven over/out of/in twenty of the students have passed the flight test.二十个学生中有七个通过了飞行测试。3) 带分数:“整数+ and + 分数部分”。Two and a quarter inches of rain fell over the weekend.周末期间的降雨量达二又四分之一英寸。2. 小数:小数总是用阿拉伯数字表达。小数点后不论有多少位都不能用逗号分开,但小数点之前的数依然按照三位一个逗号的原则书写。0.786432 120,372.428注意:小数点前的数按普通基数词的读法读,小数点后的数每一位都要单独读。15.503 读作fifteen point five zero three0.05 读作zero point zero five3. 百分数:百分数中的数目用阿拉伯数字,后接percent或百分号(%),在专业统计或表格中常用%代替percent,在句首时则用英语单词书写。I have invested 40 percent of my income.我把40%的收入用作投资了。Farmers’ income has increased by 30%.农民的收入已经增加了30%。4、 倍数:表示倍数时,一倍用once,两倍 用twice/double,三倍以上用“基数词+ times”。1)“倍数 + as many/much … as …”My deskmate claims to have twice as many stamps as I.我同桌声称他的邮票是我的两倍。This computer costs three times as much as that one.这台计算机的价格是那台的三倍。2)“倍数 + the size of …”用法与size相同的名词常见的有weight(重量),height(高度),depth(深度),width(宽度),age(年龄),length(长度)等。Our playground is five times the size of theirs.我们的操场是他们的五倍大。This street is twice/double the width of that one.这条大街是那条大街的两倍宽。3)“倍数 + what从句”The value of the house is double what it was.这所房子的价值是原来的两倍。People’s average income is almost five times what they earned ten years ago.人们的平均收入是十年前的五倍。4)“倍数 + 比较级 + than”The room is twice larger than ours.这间房子比我们的房子大两倍。This ball seats three times more people than that one.这个大厅能坐的人数是那个大厅的四倍。5)“比较级 + than … + by + 倍数/程度”The line is longer than that one by twice.这根线是那根线的两倍长。The population of China is larger than that of the US by over 6 times.中国人口是美国人口的六倍多。5、四则运算:1)加法:在口语中,小数目的加法常用and代表“+”,is 或 are 代表“=”。在正式的场合或较大数目的加法用plus代表“+”,equals或is 代表“=”。7+4=11 Seven and four is/are eleven.13+12=25 Thirteen plus twelve equals/is twenty-five.2) 减法:在口语中,小数目的减法用“Take away + 减数 + from + 被减数 + and you get + 余数”“减数 + from + 被减数 + leaves/is + 余数”在正式的场合或较大数目的减法用minus 代表“—”,equals 代表“=”。12-5=7 Five from twelve leaves/is seven. /Take away five from twelve and you get seven.21-7=14 Twenty-one minus seven equals fourteen.3) 乘法:在口语中,小数目的乘法的乘数用复数形式,用are 代表“=”。大数目的乘法用times代表“×”,is/makes 代表“=”。在正式的场合下用multiplied by 代表“×”,equals 代表“=”。4×5=20 Four fives are twenty326×238=77588Three hundred and twenty-six times two hundred and thirty-eight is/makes seventy-seven thousand five hundred and eighty-eight.Three hundred and twenty-six multiplied by two hundred and thirty-eight equals seventy-seven thousand five hundred and eighty-eight.4) 除法:小数目的除法:用divided by 代表“÷”,equals 代表“=”。“被除数 + divided by + 除数 + equals + 商”;“除数 + into + 被除数 + goes + 商”32÷4=8 Thirty-two divided by four equals eight.Four into thirty-two goes eight.大数目的除法:用divided by 代表“÷”,equals 代表“=”。216÷8=27Two hundred and sixteen divided by eight equals twenty-seven.6、比率:一般来说表示比率都用阿拉伯数字(包括句首的情况),但在非专业性的文字中,也可用英语单词的形式。The ratio of 7 to 4 is written 7:4 or 7/4.七比四写作7:4或7/4。You have a fifty to fifty chance of success.你成功的机会只有一半。7、编号:用基数词时 名词 + 基数词 World War Ⅰ/Page 8/Room 109…用序数词时 the + 序数词 + 名词 the First World War8、年代与几十几岁:通常是逢十的基数词用作复数形式。表示年代的数词前用定冠词 in the 90s;表示岁数的数词前用形容词用物主代词 in one’s twenties9、约数:1)表示“大约”可以用about/some/around/nearly/something like/more or less,用or so 表示“左右、大约”置于数词之后。The man in rags is about/some sixty years old.The man in rags is sixty years old or so.那个衣衫褴褛的男子大约有六十岁/六十岁左右。Peter is something like thirty.皮特大约有三十岁。2)“多于、超过”用more/than/over/above;“少于、不超过”用less than。She was more than/less than forty when she got married.她结婚时有四十多岁/不到四十岁。3)其他半天(小时)half a day=a half day; half an hour=a half hour一个半 a day and a half=one and a half days两天半 two days and a half=two and a half days一两天……one or two days=a day or two两三天/周/个苹果 a couple of days/weeks/apples…三番五次 again and again; repeatedly; time and (time) again; over and over again; time after time三年五载 from three to five years; in a few years三三两两 in twos and threes; in knots英语资源合集资源合集: &歌曲TED: & 演讲电影纪录片: &英语教学:开心英语: &
天天天晴9080
在图中(以及在表15-l中)你还可以看到边际收益甚至可以是负的。当价格对收益的影响大于对产量的影响时,边际收益是负的。在这种情况下,当企业多生产一单位产品时,尽管企业销售了更多单位产品,但价格下降之大足以引起企业的总收益减少。利润最大化我们已经考虑了一个垄断企业的收益,现在可以考察这种企业如何实现利润最大化。我们还记得第一章中的经济学十大原理之一是,理性人考虑边际量。这个结论对垄断者和对竞争企业同样正确。这里我们把边际分析的逻辑用于分析垄断者如何决定生产多少的问题。图15-4画出一个垄断企业的需求曲线、边际收益曲线和成本曲线。所有这些曲线看来都是熟悉的:需求和边际收益曲线像图15-3中的这些曲线,成本曲线像我们在第十三章中所介绍并在第十四章中用于分析竞争企业的成本曲线。这些曲线包含了我们确定利润最大化垄断者将选择的产量水平所需要的全部信息。首先假设,企业在低产量水平上生产,例如Q1。在这种情况下,边际成本小于边际收益。如果企业增加一单位产量,增加的收益将大于增加的成本,利润将增加。因此,当边际成本小于边际收益时,企业可以生产更多单位产品来增加利润。
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