This table allows students to categorize numbers as being rational, irrational, natural, whole and/or integer. When teaching this, students begin by identifying whether the number is irrational or rational (the gray columns). If the number is irrational, then they stop there (some draw a line through the non-gray columns). If the number is rational, then they move left to right to determine if and in what other number systems the number is a part of. This handout is especially helpful for lower-level students or students who identify themselves as "linear learners."