Write the numbers 21 to 99 with a hyphen. For example:
Hyphens are also used in larger numbers in the thousands and millions places. For example:
45,000 > Forty-five thousand
189,000 > One hundred [and] eighty-nine thousand
234,362,000 > Two hundred [and] thirty-four million, three hundred [and] sixty-two thousand
Note that American English does not use the [and] with larger numbers.
Hyphenate fractions when they are used as adjectives or adverbs. For example:
I had a one-quarter interest in the company.
Opinion varies on whether fractions used as nouns should be hyphenated.
There are no hard and fast rules although most tend to write smaller numbers in words and use numerals for larger numbers. For example:
However, you should be consistent. For example:
Frank and Blake raised five pounds each but, remarkably, Sue raise £1,250.
Would be better written
Frank and Blake raised £5 each but, remarkably, Sue raise £1,250.
It is common to use the convention that applies to the larger number for all the numbers.
Alternating words and numeral forms is sometimes required for clarity. For example:
There were five eight-year-old boys at the party.
There were 5 eight-year-old-boys at the party.