There have been a number of recent questions concerning when to use hypens. The following is an excerpt from The Economist magazine's style guide.
© The Economist Newspaper Limited 2004
Use hyphens for:
1. FRACTIONS (whether nouns or adjectives): two-thirds, four-fifths, one-sixth,...
ESL Common English Questions and Answers - Archived Posts
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taiwandave
4 yr 165 days ago
Nouns, Adverbs, Verbs, Numbers, Universities, Prepositional Verbs, Prefixes, Dates, Hyphens, Quotation Marks, Grammar, Constructions