Q. If I’m expressing a range of percentages in a statistics-heavy paragraph of academic social sciences prose, does the percent sign commute? For example, does “50 to 55% of respondents” make sense, or should I use a percent sign after each numeral, making it “50% to 55%” instead? What about other units of measurement? Is “from 100 to 110km” better or worse than “from 100km to 110km”?

A. Please see CMOS 9.17: “For expressions including two or more quantities, the abbreviation or symbol is repeated if it is closed up to the number but not if it is separated: 35%–50%, but 2 × 5 cm.” (See 10.52 and 10.61 for when to use a space before a symbol.)