What is a ruler postulate?

Answer 1

Ruler PostulateThe ruler postulate states that:

1. Every point on a line can be paired with a real number.
2. The number associated with a point A on the line is called the coordinate of A.
3. Two arbitrary points can be paired with the numbers 0 and 1, defining the length of a unit.
4. The distance between any two points A and B is designated AB.
5. The distance between two points A and B can be found by taking the absolute value of the difference of their coordinates: AB = |A - B|. Note that this implies that a distance is always positive.