# Segment Postulates

- Author:
- Judith Hilinski, Duane Habecker

- Topic:
- Line Segment

**Two basic postulates for working with segments and lengths are the Ruler Postulate and the Segment Addition Postulate.**

## Segment Addition Postulate Defined

**If three points A, B and C are ______________________, and B is ________________ A and C, then __________________________________**

## Ruler Postulate Defined

**The distance between ______ points on a number line can be found by taking the absolute value of the ________________ of their __________________________.**

**Launch the PLIX activity and click the "Challenge Me" button. **

## Segment Addition Challenge

**Use a broken centimeter ruler to determine the length of each line.**

## Ruler Postulate (centimeters)

## Example Finding the length of segment A

**Grab and move the ruler by clicking and holding on the red point. Adjust the angle of the ruler by clicking and holding the blue point. Line the ruler (top) so that the left endpoint of the segment is at 9. The right endpoint of the segment ends at 12.9. So to find the length of segment a, (12.9 - 9 = 3.9) The length of segment a is 3.9. I can check the box to see if I'm correct.**