Ruler Postulate Summary

1. On a number line, every point can be paired with a number and every number can be paired with a point.
2. The number associated with a point A on a number line is called its coordinate.
3. The distance between two point A and B is denoted by AB. (Note: there is NO line segment symbol!)
4. The length of a line segment is a positive number (in geometry).
5. The distance between two points on a number line can be found by taking the absolute value of the difference of their coordinates.

The Ruler Postulate (in simplified terms)

Suppose we have the points R and S on a number line where the coordinate of R=r and the coordinate of S=s. Then the Ruler Postulate tells us how to find the length RS. We subtract the coordinates (in any order) and take the absolute value.