英语分数、小数、百分数的用法

1. 表示分数时，分子须用基数词，分母须用序数词。当分子是1以上的任何数时，分母须用复数形式。
1/2: one half 或a half (不读为 one second)
1/3: one third 或 a third
2/3: two thirds
1/4: a quarter 或 one quarter
3/4: three quarters 或 three fourths
2/5: two fifths
5 3/5: five and three fifths
2 1/4: two and a quarter
7 3/4: seven and three quarters
1 1/2: one and a half

小数的英文写法如下:
6.4 读作six point four
67.89 读作 sixty-seven point eight nine 或 six seven point eight nine
0.05 读作 zero point zero five

百分数的英文写法如下:
43% 读作 forty-six per cent

[注] per cent 在美式英语中通常没有空格，写为 percent。

2. 以下是分数和百分数的用法：
1) 作主语
Over three-fifths of such projects have failed to meet expectations. 这类计划中超过五分之三未能达到预期目标。
Only ten percent of the islanders here are well educated. 这儿的岛民只有百分之十受过良好教育。

2) 作宾语或介词宾语
He spent a quarter of his salary on rent each month. 他每月要花四份之一的收入在房租上面。
This accounts for 28.8 percent of the total number of civil servants. 这个占公职人员总数的28.8%。

3) 作定语
The cost is only one-third the market price. 成本只是市场价的三分之一。 (注意：分数词作定语时，后边需要有定冠词 the)
By 2020 there will be a 10 percent drop in the 20-30 age group. 到2020年，20-30年龄组的人将下降10%。

4) 作状语
The output will be 20 percent higher than last year. 产量将比去年高出百分之20。
The new train ran 50% faster than before. 新火车比以前快50%。

5) 作表语
6 is 2 percent of 300. 6是300的百分之二。

3. 问百分之几可以用 what percent 或 what percentage 如:
What percentage of students were absent? — Twenty percent. 学生缺席的比例是多少？－－ 百分之二十。
What percent of the population will vote for Obama. 百分之多少的人会投票给奥巴马？

4. 分数作主语时，谓语动词形式应与of后的名词保持一致。
Two-fifths of the books here are worth reading. 这里有五分之二的书值得看。
Two-thirds of the crop was damaged during the storm. 三分之二的庄稼被暴雨毁坏。

5. 百分比percent (或per cent, %) 作主语时的主谓一致。
1) 百分比加不可数名词或单数名词时，谓语动词一般用单数形式。
70 percent of the fund was provided by the government. 70％的资金由政府提供。

2) 百分比加集体名词，则谓语动词可以用单复数形式均可。
What per cent of the population read/reads books? 识字的人占人口的百分之几?

3) 百分比加复数名词，则谓语动词用复数形式。
65% of children play computer games. 65%的小孩子玩电脑游戏。