A few handy rules about numbers and numerals:
Don’t put the letter A in front of numeric values. Don’t say, “A 127 people chose option b,” or “the suit cost a $100.” Just say, “There were 127 people who chose option b,” or “the suit cost $100.” Be aware, too, that you can’t begin a sentence with a numeral:
Wrong: “127 people chose option B.”
Correct: “One hundred and twenty people chose option B” OR “A total of 127 people chose option B.”
The second choice is really better because you really aren’t supposed to spell out numbers over a hundred. Some editors argue that numerals shouldn’t be used in dialogue because people don’t “speak” in numerals, but there is nothing objectionable, according to Chicago style, that prevents a writer from using numerals in dialog. The main concern is you want to be clear and consistent. No one want to read a sentence like “Hey, I got seventeen thousand, eight hundred, and fifty-six downloads on Amazon.” This is so much easier on the eyes:
- “Hey, I saw you had 236 five-star reviews on Amazon—that’s great,” she said.
Chicago recommends using numerals for dates and in brand names like 7-Eleven.
- “I graduated class of ’96.” (make sure your curly quote curves like a backward c)
- “Let’s ride down to 7-Eleven and get eight hot dogs.”
Also be mindful when writing monetary values. Don’t write “$100 dollars,” just “$100.” You have already implied dollars by using the $ sign.