fifteen minus five is ten。算式15-5=10謂語動詞用單數is。英語中加減乘除運算只有乘法可以用複數的謂語動詞are/equal，其餘都用單數is/equals。例如：

1.five and five is 10(5+5=10)

2.2 multiplied by 2 is/are 4(2*2=4)

3.10 minus five is five(10-5=5)

4.10 divided by 2 is 5 (10/2=5)

數詞的一些特殊用法

1.表示四則運算

3+6=9 Three plus six is nine.

5+5=? How much is five plus five?

10-5=5 Ten minus five is five.

4x2=8 Four times two is eight.

20÷4=5 Twenty divided by four is five.

2.表示編號

Lesson 5 (the fifth lesson) Class 3 (the third class)

Room 308 page 416

3.表示世紀、年代

（在）20世紀 (in) the 20th century

（在）30年代 (in) the thirties

（在）20世紀90年代 (in) 1990s

（在）1983年 (in) 1983

4.表示日期

（在）6月1日 (on) the first of June

(on) June the first

(on) June 1st

（在）1983年5月1日 (on) May 1st, 1983

注意點：在“年”“月”前要用介詞in。在“...月...日”或“...年...月...日”前用介詞on。

5.表示時刻

6:00 six o'clock 或 six

8:10 ten past eight 或 eight ten

9:45 a quarter to ten 或 nine forty-five

10:55 five to eleven 或 ten fifty-five

11:30 half past eleven 或 eleven thirty

注意點：在時刻前用介詞at

6.表示歲數

She is fifteen (years old). 她15歲了。

He went to school at (the age of) seven. 他7歲上學。

7.分數、小數、百分數的表示

①分數：分數是由基數詞、序數片語成。分子用基數詞，分母用序數詞，分子除1以外，序數詞都用複數形式。

1/3 三分之一 one/a third 2/3 三分之二 two-thirds

7/10 十分之七 seven-tenths

2 2/3 二又三分之二 two and two-thirds

②小數：小數點是point，零是zero，小數點以後的數按個位基數詞依次讀出。

0.7 zero point seven

1.55 one point five five

13.98 thirteen point nine eight

③百分數：百分數由基數詞加percent構成。

5% five percent

45% forty-five percent

350% three hundred and fifty percent

8.倍數的表示

①表示增加一倍

The output of cars has doubled.

汽車產量增加了一倍。

②表示增加兩倍

The output of cars has been increased three times as against 1998.

汽車產量與1998年相比增加了兩倍。

③The output of cars is three times greater than that of last year.

汽車產量比去年增加了3倍。

④表示有...幾倍大

It is four times as large as Europe.

它有歐洲的四倍大。

9.“every other...”的表達方式。

every other day 每隔一天 every three days 每隔兩天

every other week 每隔一週 every third day 每逢第三天