Referring to an exact part of something: fractions

2.257 When you want to indicate how large a part of something is compared to the whole of it, you use a fraction, such as 'a third', followed by 'of' and a noun group referring to the whole thing. Fractions can also be written in figures (see paragraph 2.265).

2.258 When you express a fraction in words, the way you do so depends on whether the fraction is singular or plural. If it is singular, you write or say an ordinal number or the special fraction terms 'half' or 'quarter', with either the number 'one' or a determiner such as 'a' in front of them. The fraction is linked to a noun group by 'of'.

This state produces a third of the nation's oil.

...a quarter of an inch.

You can take a fifth of your money out on demand.

A tenth of the working population will be writing material for computers.

Forests cover one third of the country.

...one thousandth of a degree.

...one quarter of the total population.

An adjective can also be placed after the determiner and before the fraction.

...the first half of the twentieth century.

I read the first half of the book.

...the southern half of England.

...in the last quarter of 1980.

2.259 If you are using 'half' in front of a pronoun, you still use 'of' after the 'half'.

Nearly half of it comes from the Middle East.

More than half of them have gone home.

Half of us have lost our jobs.

Note that when the fraction 'a half' is used with 'of' as a quantifier you usually write or say it as 'half' without a determiner. 'A half' and 'one half' are rarely used.

They lost half of their pay.

Half of the people went to private schools.

I had crosses more than halt of America.

2.260 If the fraction is plural, you put a cardinal number in front of a plural form of the ordinal number or special fraction word 'quarter'.

...the poorer two thirds of the world.

The journey is going to take three quarters of an hour.

...four fifths of the money.

Nine tenths of them live on the land.

..3 millionths of a centimetre.

When 'half' is used with whole numbers or amounts, it is used with the determiner 'a'.

...one and a half acres of land.

...four and half centuries.

agreement with verb 2.261 When you talk about fractions of a single thing, you use a singular form of a verb afterwards.

Half of our work is to design programmes.

Two thirds of the planet's surface is covered with water.

Two fifths of the forest was removed.

However, when you talk about fractions of a number of things, you use a plural form of a verb afterwards.

Two thirds of Chad's exports were cotton.

A quarter of the students were seen individually.

Nearly half of Jakarta's one million workers are in the informal sector.

fractions as pronouns 2.262 When it is clear to your listener or reader who or what you are referring to, either because of the context or because you and your listener or reader know what is meant, you can use fractions as pronouns without the quantifying 'of' and noun group after them.

Of the people who work here, half are French and half are English.

Two thirds were sterilized.

One fifth are appointed by the Regional Hearth Authority.

numbers followed by fractions 2.263 Besides their use as quantifiers linked by 'of' to a noun group, fractions can, also be used after a whole number or amount plus 'and', with a noun placed after the fraction. The noun must be plural even if the number is 'one'.

You've got to sit there for one and a half hours.

...five and a quarter days.

...more than four and a half centuries ago.

If you are using 'a' instead of 'one', the 'and' and m fraction come after the noun.

...a mile and a half below the surface.

...a mile and a quarter of motorway.

'half' as predeterminer 2.264 Besides being used with 'of' as a quantifier, 'half' can also be used as a predeterminer, (see paragraph 1.236), directly in front of a determiner.

I met half the girls at the conference.

The farmers sold off half their land.

...half a pound of coffee.

...half a bottle of milk.

Note that 'half' is always used with 'of' before a pronoun (see paragraph 2.259).

fractions expressed in figures 2.265 You can write a fraction in figures, for example '1/2', '1/4', '3/4' and '2/3'. These correspond to 'a half', 'a quarter', 'three quarters' and 'two thirds' respectively.

2.266 Fractions are often given in a special form as a number of hundredths. This type of fraction is called a percentage. For example 'three hundredths', expressed as a percentage, is 'three per cent'. It can also be written as 'three percent' or '3%'. 'A half' can be expressed as 'fifty per cent', 'fifty percent', or '50%'.

90 percent of most food is water.

About 20 per cent of student accountants are women.

Before 1960 45% of British trade was with the Commonwealth.

You can use percentages on their own as noun groups when it is clear what they refer to.

Ninety per cent were self employed.

...interest at 10% per annum.