5.+Measuring+Segments

=Measuring Segments= Objective: To find the lengths of segments.

Visit Standards page to identify numbers. NCTM Standards: 1, 2, 3, 4 CT Mathematics Standards: 1.3a, 2.1a(1), 2.2, 3.2
 * Standards **

//The following can be found at [|http://spartans.sstx.org/~krutkowski/notes%20and%20resources/chapt1refweb/chapter1reference.html.] //

1) You can pair each point on a line with a real number. The number that corresponds to the point is called the point's //coordinate//. 2) To find the distance between two points, subtract their coordinates, and take the absolute value (make the answer a positive number).
 * The Ruler Postulate **

Two segments with the same length are //congruent segments.//

Here is a good discussion about the Ruler Postulate: []

** Segment Addition Postulate﻿ ** If three points A, B, and C are collinear and B is between A and C, then AB + BC = AC.



If AB = 2X - 8, BC = 3X - 12, and AC = 60, find the value of x. Then find AB and BC.
 * 1) AB + BC = AC
 * 2) (2X - 8) + (3X - 12) = 60 (Substitute.)
 * 3) 5X - 20 = 60 (Simplify.)
 * 4) 5X = 80 (Add 20 to both sides.)
 * 5) X = 16 (Divide both sides by 5.)

If X = 16, then by substitution: AB = 2(16) - 8 = 24 <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">BC = 3(16) - 12 = 36

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">To check, 24 + 36 = 60.

Use the manipulative on this website to prove the segment addition postulate. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">[]  ﻿Post your results in the discussion tab.

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 120%;">Let's review with this power point presentation: []