What is meant by 'common denominator'?

A common denominator refers to the situation in which two or more fractions share the same denominator. This concept is fundamental when performing operations such as addition or subtraction with fractions, as it allows for the direct comparison of their numerators and simplifies those calculations.

For example, if you have the fractions 1/4 and 1/6, the common denominator would be 12, since 12 is the smallest multiple that both 4 and 6 divide evenly into. By converting both fractions to have this common denominator (1/4 becomes 3/12 and 1/6 becomes 2/12), you can easily perform operations such as addition (3/12 + 2/12 = 5/12).

In contrast, the other options describe concepts that do not accurately define what a common denominator is. While having different numerators refers to how fractions can vary, it does not pertain to denominators. A fraction expressed as a decimal does not capture the essence of common denominators, and the process of finding equivalent fractions relates to scaling fractions rather than finding a common denominator. Thus, the correct answer highlights the necessity of having a shared denominator to facilitate operations involving multiple fractions.