Writing Numbers !

I didn't realize that there was so many rules for writing numbers. Below are three of the sixteen rules that I found. The rest of the rules can be found HERE.

Rule 1.
Spell out single-digit whole numbers. Use numerals for numbers greater than nine.

Correct Examples:
I want five copies.
I want 10 copies.

Rule 3.
Always spell out simple fractions and use hyphens with them.

Examples:
One-half of the pies have been eaten. A two-thirds majority is required for that bill to pass in Congress.

Rule 14.
Use noon and midnight rather than 12:00 P.M. and 12:00 A.M.