序數詞“三注意”。

一)序數詞的構成及基本用法。注意：序數詞一般以與之相應的基數詞后加-th 構成，少數幾個需特別記憶。為方便大家記憶，請看下面口訣。

基變序，有規(guī)律，first, second, third要牢記;

其它變化有公式，基數詞尾加-th;

eight去t , nine去e;

從twenty, thirty到ninety, 需變y為ie;

five和twelve, 需將ve變f;

若是遇到“幾十幾”，只變個位就可以。

另外，注意：序數詞前要加定冠詞the, 在句中作定語放在所修飾的名詞前。如：December is the twelfth month of the year. 十二月是一年中的第12個月。

挑戰(zhàn)中考：( )15. Thursday is the _____ day of the week. (five)

( 用所給詞的適當形式填空)

( )16. He believed his lucky number was ten, so he decided to live on the ____ floor.

A. lowest B. ten C. tenth

( )17. I have made ____ dumplings. Now I’m making the ___ one.

A. twenty; twentieth-first B. twenty; twenty-first

C. twentieth; twenty-first D. twenty; twenty-one

二)序數詞與冠詞a/an連用。注意：序數詞前加不定冠詞a/an, 表示“又一”、“再一”的意思。如：Please try it a second time. 請再試一試。但基數詞與more連用，并放在more前，表示“另外有”、“還有”的意思。如：I’ll take one more (=another) pencil. 我還要一支鉛筆。We ’ve just started! There were twenty more trees to be planted!我們才剛開始呢!還有20棵樹要栽呢!

挑戰(zhàn)中考：

( )18.Time is not enough for so much work. ____ people are needed, I think.

A. Other two B. Only two C. Two more D. Two others

( )19. Both of the two rulers are broken. I want to buy a ___ one.

A. three B. third C. forth D. 不填

三)分數的表達法。注意：分數以基數詞和序數詞合成的。分子用基數表示，分母用序數詞表示，分子大于1，分母要用復數(-s)。如：1/3(三分之一) ：one third 2/3 :two thirds

挑戰(zhàn)中考：

( )20. This is a big class, and ____ of the students are girls.

A. two third B. second three C. two thirds D. two three

( )21. –What’s one fourth and a half , do you know?

--Yes, it’s ______. )

A. two sixths B. three fourths C. one three D. three sixths

練習參考答案：1.A 2.A 3.D 4.D 5.C 6.D 7.B 8.A 9.A 10.B 11.D 12.D 13.A 14.B 15.fifth 16.C 17.B 18.C 19.B 20.C 21.B

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