Segment Addition Postulate: Find AD given BC=6, BD=14, AC=9

Published on May 8, 2026

Geometry

Learn to find the length of AD using the Segment Addition Postulate and the given lengths of segments BC, BD, and AC.

Question

Answer

The problem states that point is between points and , and point is between points and . This means the points are arranged in the order along a line.
We are given the following lengths:
  • •
  • •
  • •
We need to find the length of .
Since is between and , we can write the relationship:
We are given and . Substituting these values into the equation:

Subtracting 6 from both sides:

Since is between and , we can write the relationship:
We are given and . Substituting these values into the equation:

Subtracting 6 from both sides:

Now we need to find the length of . Since the points are in the order , we can express as the sum of the lengths of the segments:
We have found the lengths of , , and :


Substituting these values into the equation for :


Alternatively, we know that and .
We are given and .
Since is between and , .
.
Since is between and , .
We are given and .
.
The length can also be expressed as .
We found and we are given .
.
The final answer is .