What is a term that refers to a pair of equal or equivalent ratios?

The term that refers to a pair of equal or equivalent ratios is a proportion. A proportion states that two ratios are equivalent, which means that the relationship between the two quantities represented in the ratios is the same. For instance, if you have the ratio 1:2 and another ratio 2:4, these can be expressed as a proportion because they represent the same relationship.

In mathematical terms, a proportion can be written in the form a/b = c/d, where a, b, c, and d are quantities and the cross products (ad and bc) are equal. This concept is fundamental in mathematics, particularly in solving problems involving similar figures, scaling, and comparing quantities.

The other terms do not correctly represent the concept of two ratios being equal: a fraction defines a single quantity expressed as a part of a whole, an equation refers to a statement that two expressions are equal, and a ratio indicates a relationship between two numbers, but does not inherently imply equivalence between two ratios.