Mister Smith is sixty^① years old and yesterday was his 60th^② birthday.He still remembers in the 1990s^③ when he was in his thirties^③，he drank dozens of^④ bottles of beer a day.However，he spent thousands of^④ dollars in hospital.Later，two fifths^⑤ of his spare time was spent in taking exercise.

[规则感悟] ①数词的基本形式为基数词。②表示数词的顺序往往用序数词。大部分是在基数词的基础上加-th。以-y结尾的基数词变序数词，把-y变成-ie再加-th。③“in the＋逢十的基数词的复数”表示“在某个世纪几十年代”。“in one’s＋逢十的基数词的复数”表示“在某人几十多岁时”。④具体数字＋dozen/score/hundred/thousand/million 等词时，后面直接加名词复数；表示笼统数目时，用dozens/scores/hundreds/thousands/millions of＋名词复数。⑤分数表达：分子用基数词，分母用序数词。当分子大于1时，分母序数词加-s，如：1/3：one third,2/3：two thirds。

1．易错基数词

thirteen十三 fourteen十四 fifteen十五

eighteen十八 nineteen十九 twenty二十

thirty三十 forty四十 fifty五十 ninety九十

2．易错序数词

first第一 second第二 third第三 fourth第四

fifth第五 eighth第八 ninth第九 eleventh第十一 twelfth第十二

3．序数词的使用

(1)序数词在句中主要作定语，一般情况下序数词前要加定冠词。

This is the second intangible cultural heritage block in Guangzhou.

这是广州第二个非物质文化遗产街区。

(2)序数词前有时加不定冠词，表示“又一、再一”，相当于another。

Would you like a second cup of tea?

你还想再来一杯茶吗？

(3)有时序数词作状语，不加冠词。

He came out first in the contest.

他在比赛中获得第一名。

对点练习

1．Peter got a model ship from his uncle on his thirteenth(thirteen) birthday.

2．Two thirds(three) of the students in our class have been to Disneyland.

3．Linda，there are too many mistakes in the ninth(nine) line of your passage.

4．He made quite a few friends during his twenties(twenty)．

5．It is reported that the earthquake has left thousands(thousand) of people homeless.