As we all know Math concepts build on each other. When it comes to Measuring Segments and the Segment Addition Postulate there are multiple lessons we must pull together to teach this lesson. The videos below do an excellent job of explaining measuring segments using the following methods.
Ruler Postulate 
Segment Addition Postulate 
Pythagorean Theorem 
Distance Formula 
Use a Manipulative to Teach the Measuring Segments
My advice would be to use blocks or cut outs like these to teach this lesson. I think establishing the connection between these realworld things and the algebra behind the geometry make these postulates much easier to learn. If you just go in with and number line and some numbers on the chalk board it probably won’t stick. I even think the measuring segments worksheets you use need to have more realistic pictures and problems in them.
Give them the squares that they can touch and manipulate. They do not have to be anything fancy. You can actually just give them square pieces of precut paper to play around with. Give them a ruler or yard stick, things they can touch and see themselves actually doing in the real world.
The Pythagorean Theorem and the Segment Addition Postulate
We also included a segment addition postulate worksheet below. These will include the problems involving distance formula, the Pythagorean Theorem, and the ruler postulate.
We also are giving you a Measuring Segments Worksheet, Exit Quiz, Bell Work Assignment, a Power Point Presentation, and some Segment Addition Postulate Guided Notes!
These Postulates Come Up Over and Over Again
Make it a lesson they won’t forget because these things come up over and over again in other lessons like…
 Absolute Value
 Constructions
 Operations with Complex Numbers
 Simplifying Radicals
 Irrational Numbers
 Fractions
 Pythagorean Theorem
 Square Roots
The more students hear how to develop strategies, the better they become at doing so.
Seeing these concepts used helps students make connections about the way all math concepts are related.
Here are your Free Resources for this Lesson!
Segment Addition Postulate Worksheet, Word Docs & PowerPoints
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Segment Additions Postulate  Measuring Segments PDFs
13 Assignment Student Edition Measuring Segments ( FREE )
13 Assignment Teacher Edition  Measuring Segments (Members Only)
13 Bell Work Student Edition  Measuring Segments ( FREE )
13 Bell Work Teacher Edition  Measuring Segments (Members Only)
13 Exit Quiz Student Edition Measuring Segments ( FREE )
13 Exit Quiz Teacher Edition  Measuring Segments (Members Only)
13 Guided Notes SE  Measuring Segments ( FREE )
13 Guided Notes Teacher Edition  Measuring Segments (Members Only)
13 Lesson Plan  Measuring Segments and the Segment Addition Postulate (Members Only)
13 Online Activities  Segment Addition Postulate (Members Only)
13 Slide Show  Measuring Segments ( FREE )
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