# Ruler Postulate Summary

- On a number line, every point can be paired with a number and every number can be paired with a point.
- The number associated with a point A on a number line is called its
**coordinate**.
- The distance between two point A and B is denoted by AB. (Note: there is NO line segment symbol!)
- The length of a line segment is a positive number (in geometry).
- 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.

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