Manuscript Preparation, Copyediting, and Proofreading

Q. Dear CMOS, I am wondering about how to handle competing rules. For example, numbers are written in numeral form when used as percentages. However, if that number is starting a sentence, it would be spelled out. For example: 27 percent of the students passed. Or: Twenty-seven percent of the students passed. Which would be advised? Thank you for any clarification you can provide.

A. Chicago recommends spelling out a number at the beginning of a sentence. It might help not to think in terms of “competing rules,” which leaves a person feeling helpless; instead try to think in terms of rules that have many exceptions. This is normal, both in CMOS and in life!