Using Numbers, Writing Lists - Guide to Grammar
http://www.guidetogrammar.org/grammar/numbers.htm
WEBUse numerals, however, when the number modifies a unit of measure, time, proportion, etc.: 2 inches, 5-minute delay, 65 mph, 23 years old, page 23, 2 percent. Use numerals for decimals and fractions: 0.75, 3.45, 1/4 oz, 7/8 in. (Notice that abbreviations are always written in the singular form whether they would be expressed as plurals or not ...
DA: 16 PA: 17 MOZ Rank: 8