How is a rate defined in mathematical terms?

A rate is defined as a ratio that compares two quantities measured in different units. This fundamental concept allows us to express the relationship between varying types of measurements, such as distance to time or cost to quantity.

For instance, when we say a car travels at a speed of 60 miles per hour, we are comparing the distance traveled (in miles) to the time taken (in hours). It highlights how many units of one measure correspond to a single unit of another measure. This is essential in fields like physics, economics, and everyday situations where understanding how different metrics relate to one another is necessary for making informed decisions and calculations.

In this context, the other options do not fulfill the definition of a rate because they either involve quantities of the same unit, do not correctly describe a ratio, or focus on specific measurements without indicating the necessity of comparison between different units.