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

What is a proportion?

1. A ratio that compares two quantities with the same measurement

2. An equation that shows two ratios are equal

3. The average of a set of numbers

4. The middle value of a dataset

The correct answer is: An equation that shows two ratios are equal

A proportion is fundamentally characterized as an equation that shows two ratios are equal. In mathematical terms, a proportion can be represented in the form \( \frac{a}{b} = \frac{c}{d} \) where \( a \), \( b \), \( c \), and \( d \) are numbers. This equality indicates that the relationship between the two pairs of numbers is consistent, demonstrating that the two ratios are equivalent. Proportions are essential in solving problems involving scaling, comparing quantities, and working with similar figures. This understanding is critical in applications where you need to maintain a consistent ratio between two sets of values, such as in recipes, map reading, or financial calculations. While the other definitions may have relevance in mathematics, they do not capture the specific nature of a proportion. For instance, a ratio that compares two quantities with the same measurement does not involve the equality of ratios, while the average of a set of numbers and the middle value of a dataset are specific measures of central tendency, not related to the concept of proportionality. Thus, the core definition of a proportion aligns perfectly with the idea of an equation equating two ratios.