An ordered pair is defined as which of the following?

• A. An ordered pair is a pair of numbers for which order is important.
• B. It is a set of numbers without order.
• C. It is always two equal numbers.
• D. It is about ratios only.

Answer: (A)

An ordered pair is a pair of elements where the position matters: the first component and the second component are distinct, so swapping them yields a different pair. This is why (3,4) is not the same as (4,3); the first entry corresponds to the first coordinate and the second to the second. This differs from a set, which lists elements without regard to order, and from a ratio, which describes a relationship rather than a specific ordered pair. The two elements need not be different—(5,5) is still an ordered pair. Using parentheses signals the order; curly braces would denote a set. Therefore, an ordered pair is a pair of numbers for which order is important.