Two basic postulates for working with segments and lengths are the Ruler Postulate and the Segment Addition Postulate.
If three points A, B and C are ______________________, and B is ________________ A and C, then __________________________________
If three points A, B and C are collinear, and B is between A and C, then AB + BC = AC
The distance between ______ points on a number line can be found by taking the absolute value of the ________________ of their __________________________.
The distance between two points on a number line can be found by taking the absolute value of the difference of their coordinates.
Use a broken centimeter ruler to determine the length of each line.
Grab and move the ruler by clicking and holding on the red point. Adjust the angle of the ruler by clicking and holding the blue point. Line the ruler (top) so that the left endpoint of the segment is at 9. The right endpoint of the segment ends at 12.9. So to find the length of segment a, (12.9 - 9 = 3.9) The length of segment a is 3.9. I can check the box to see if I'm correct.