�。�2）倍數(shù)放在形容詞或副詞的比較級(jí)之前或by + 倍數(shù)用在比較級(jí)之后。如：

　　This rope is four times longer than that one.

　　They produced more products in 2001 than those in 2000 by twice.

　　The production of grain has been increased by four times this year.

　�。�3）倍數(shù)用在表示度量名詞前，其基本結(jié)構(gòu)為：倍數(shù) + the +size / length / weight … + of + 表示比較對(duì)象的名詞，也可用于倍數(shù) + what引導(dǎo)的從句中。如：

　　This room is three times the size of that one.

　　The college is twice what it was 5 years age.

　　You can't imagine that rats eat 40 to 50 times their weight.

　　6大約數(shù)的表示方法

　�。�1）用ten、dozen、score、hundred、thousand、million等數(shù)詞的復(fù)數(shù)后加of短語來表示幾十、幾百、上千、成千上萬等大約數(shù)概念。

　�。�2）dozen表約數(shù)（一打），基數(shù)詞+dozen+名詞復(fù)數(shù)(不加of)。如：two dozen pens。注意:若名詞前有the,this,those等修飾時(shí)要加of.如：one dozen of the eggs,two dozen of the eggs.

　　(3)score(20)單復(fù)數(shù)同形，通常與of連用。但時(shí)間名詞前不加of.如: one score years20年

　�。�4）用less than、under、below、almost、nearly、up to 等來表示小于或接近某數(shù)目。

　　He is good at English, so he can finish the paper in less than two hours.

　�。�5）用more than、over、above、beyond、or more等來表示超過或多于某個(gè)數(shù)目。如：

　　Peking University has a history of more than 100 years.

　�。�6）用or、or so、about、around、some、more or less等表示在某一數(shù)目左右。

　　About 50 people were present at that time.

　�。�7）用to、from … to…、between … and表示介于兩數(shù)詞。如：

　　His salary rises from 20 dollars a week to 35 dollars a week.

　　7加減乘除表示法

　　1. "加"用plus，and或add表示；"等于"用is，make，equal等詞表示。

　　2+3=? 可表示為： How much is two plus three?

　　2+3=5 Two plus three is five．

　　Two and three is equal to five．

　　Two and three make five．

　　Two added to three equals five．

　　If we add two to/and three, we get five

　　2. "減"用 minus或 take from表示

　　10－6＝?　How much is ten minus six?

　　10-6=4 Ten minus six is four．

　　Take six from ten and the remainder is four.

　　Six (taken) from ten is four．

　　3. "乘"用time（動(dòng)詞）或multiply表示

　　3X4＝? How much is three times four?

　　3X4=12 Three times four is/are twelve．

　　Three fours  is/are twelve．

　　Multiply three by four，and we get twelve．

　　Three multiplied by four makes twelve．

　　4. "除"用divide的過去分詞形式表示

　　16÷4=? How much is sixteen divided by four?

　　16÷4＝4 Sixteen divided by four is four．

　　Sixteen divided by four equals/gives/makes four．

　　If you divide 16 by 4, you get 4.

　　三.即學(xué)即練

　　1._____ people in the world are sending information by E-mail every day.

　　A.Several million           B.Many millions

　　C.Several millions          D.Many million

　　2. The number of people invited ______ fifty, but a number of them ______ absent for different reasons.

　　A.were ; was      B.was ; was

　　C.was ; were      D.were ; were

　　3. Shortly after the accident, two _____ police were sent to the sport to keep order.

　　A. dozens of       B. dozens

　　C. dozen          D. dozen of

　　4. ____ of the land in that district___ covered with trees  and grass.

　　A. Two fifth; is         B. Two fifth; are

　　C. Two fifths; is        D. Two fifths; are

　　5. It is said that the mountain is about ___ high, through which the peasants dug a hole ___ deep.

　　A. 400 foot/six hundreds metres

　　B. 400 foots/six hundred metres

　　C. 400 feets/six - hundred - metre

　　D. 400 feet/six- hundred metres

　　6. ___ cave that George has discovered in his lifetime is near the Alps.

　　A. The hundredth          B. The hundred

　　C. Hundredth            D. A hundredth

　　7. The hero of the story is an artist in his ____.

　　A. thirtieth  B. thirty  C. thirty's   D. thirties

　　8. I have to write a ____ composition every other week.

　　A. two - thousand - word

　　B. two - thousands - word

　　C. two - thousand - words

　　D. two - thousands - words

　　9.The Yellow River is ___ river in China. Hainan is ____ island.

　　A. second longest/ second China's largest

　　B. the second longest /China's second largest

　　C. second the longest/ China's the second largest

　　D. a second longest/ the China's second largest

　　10. Paper produced every year is ____ the world's production of vehicles.

　　A. the three times weight of

　　B. three times the weight of

　　C. as three times heavy as

　　D. three times as heavier as