# Segment Addition Postulate: Definition & Examples Video

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Lesson Transcript
Instructor: Karin Gonzalez

Karin has taught middle and high school Health and has a master's degree in social work.

In this lesson, we will review the definition of the segment addition postulate. We will also look at examples to clearly illustrate how this concept works in the real-world.

The segment addition postulate states that if we are given two points on a line segment, A and C, a third point B lies on the line segment AC if and only if the distances between the points meet the requirements of the equation AB + BC = AC. See Diagram 1 to gain a clearer understanding of this postulate definition.

Remember that a line segment is part of a line bound by two clear end points. It is comprised of a bunch of points between those two end points.

An easier way of stating the segment addition postulate is that if point B lies on line segment AC, then AB + BC will equal AC. That seems pretty simple, does it not?

## Examples

Let's take a look at some different examples.

Example 1:

Let us look at a line segment on our body: our leg! Our leg has an endpoint A, the top of your thigh, and endpoint C, your ankle. Imagine the length of your entire leg (from endpoint A to C) measures 25 inches and the length from point B, your knee, to endpoint C is 12 inches. According to the segment addition postulate, what would be the length of Endpoint A to point B?

AB (unknown) + BC (12) = AC (25)

AB = 25 - 12

AB = 13 inches

Example 2:

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