(Discrete structure math for computer science)

Please solve the problem in detail please.

* A rational number can be written as p / q, where p is an integer, q is an integer, and q 0. Suppose that r and r are rational numbers, and that r < r.

Prove that there is a rational number u such that r < u < r. Your proof must be constructive, and your answer must briefly explain why it is constructive.