1. Linear Measure
Objective: (1)To measure segments and determine accuracy of measurement. (2) To compute with measures.

2. Definitions
Line segment: A measureable part of a line that consists of two points, called endpoints, and all of the points between them.
Precision: The precision of any measurement depends on the smallest unit available on the measuring tool
Betweeness of points:
Between: For any two points A and B on a line, there is another point C between A and B if and only if A, B, and C are collinear and AC + CB = AB
Constructions: A method of creating geometric figures without the benefit of measuring tools. Generally, only a pencil, straightedge, and a compass are used.
Congruent: Having the same size and same shape.

3. Line Segments • • Consists of two endpoints And all points in between
Has an infinite number of points.
Since it is finite, it has a distance.
Named by the endpoints
AB or BA • A • B

4. Symbols Review AB A a Here’s a new one:
Line AB A or Point A Line a Segment AB The Length of Segment AB

5. Betweeness of Points
Point M is between points P and Q if and only if P, Q and M are collinear & if:
PM + MQ = PQ
Notice that M is between but not in the middle! There’s a difference. P • • Q • M

6. Finding the Distance Find AB if AC = 19cm and BC = 12cm 
x cm
Find AB if AC = 19cm and BC = 12cm
Since we don’t know what AB is, we’ll say, AB = x
We also know:
AB+BC=AC … now replace
x + 12 = 19
x = 7 B 
12cm
19cm C

7. Another way to find the distance
Find x if:
AB = 5x+7, BC = 3x + 2 and AC = 33m
Plug in what you know
Also AB+BC=AC
5x x + 2 = 33
8x + 9 = 33
8x = 24
3x + 2 B 
33cm
5x + 7 A

8. Continued C
8x = 24 8
x = 3
Now, just in case you’re asked to find AB or BC.
Replace the variable with 3
3x + 2
3(3) + 2
9 + 2 11 B 
33cm
5(3) + 7 22
5x + 7
15 + 7 A