California Assessment of Student Performance and Progress (CAASPP) Math Practice Exam

Which of the following defines a rate?

1. A comparison of two similar quantities

2. A number that represents an average

3. A ratio comparing two different quantities

4. An equation that shows two ratios are equal

The correct answer is: A ratio comparing two different quantities

A rate is specifically defined as a ratio that compares two different quantities, often with different units. This concept is fundamental in various mathematical and real-world applications, such as calculating speed (miles per hour), cost (dollars per item), or density (mass per volume). When considering the other options, the first choice describes a simple comparison between similar quantities, which does not encapsulate the essence of a rate. The second option refers to an average, which is a different mathematical concept focused on central tendency rather than a comparison of quantities. Lastly, the fourth option describes a proportion, which is an equation that states that two ratios are equal — again, a different concept that doesn't specify a comparison of different quantities as a rate does. Thus, the definition of a rate accurately focuses on the comparison of different quantities, confirming the correctness of the chosen answer.