Which statement best defines a ratio?

• A. A ratio is a unitless measure that compares one quantity to another.
• B. A ratio is always expressed as a percentage.
• C. A ratio is a value obtained by dividing one quantity by another; it includes rates, proportions, and frequencies.
• D. A ratio is always a fraction with the numerator smaller than the denominator.

Answer: (C)

A ratio is the value you get when you divide one quantity by another, which shows how much of one thing there is per unit of the other. This simple division captures a wide range of ideas: rates like speed (distance per time), proportions such as part to a whole, and frequencies like occurrences per population. Because you’re just comparing two quantities, the ratio can be unitless when the units cancel, or it can carry units if the quantities don’t share the same units. It isn’t limited to percentages, and it isn’t restricted to fractions where the numerator is smaller than the denominator—ratios can be greater than 1 as well. This broad, division-based definition is why it’s the best answer.