Is the circumference of a circle always, sometimes, or never rational? Learners answer questions individually and also work in groups to look at sums and products of rational and irrational numbers. They must also be able to use the Pythagorean theorem to answer several of the questions. Additionally, they consider if providing a few examples is enough to be sure a statement is always true. The detailed lesson plan includes a PowerPoint and many helpful suggestions to facilitate the lesson.