ODDS, PROPORTIONS, RATIOS

Generally spell out one through nine and use figures thereafter:

            six parts steam, 11 parts sweat

            six-to-four margin

            two to one against

            42 to 36 in favor

Odds and ratios can be written in all numerals, especially when the numeral 1 is used:

            1-in-20 chance

            10-to-1 return on investment

Spell out figures of speech such as fifty-fifty, unless the context makes numerals appropriate:

            Others thought he had a 1-in-10 chance of winning, though he considered his odds were 50-50.