Why cannot rates be expressed as a percentage?

Answer 1

It depends on the context. If the two quantities being compared (numerator and denominator) are of the same kind then the rate CAN be expressed as a percentage. For example, both are money and the rate of interest is usually expressed as a percentage.

However, the word "rate" is often used for comparisons over time. For example, speed is the rate of change of location (or distance) over time. Here the two measures - distance and time - are different and so the answer cannot be expressed as a percentage.

Answer 2

Rates cannot be expressed as a percentage because rates are typically ratios that compare two different quantities, such as distance traveled per unit of time. Percentages, on the other hand, represent a proportion out of 100. While rates can be converted to percentages by multiplying by 100, they are fundamentally different concepts and are expressed in different ways to accurately convey the relationship between the two quantities being compared.