a If three points are on a straight line, we can use the Segment Addition Postulate to calculate the total length.
B
b If we know the total length and the length of one part of the segment, we can form an equation using the Segment Addition Postulate.
A
a 8x-1
B
b 5y+20
Practice makes perfect
a The length AC is the total length of the segment, AC.
Because point B is on a straight line between A and C, we can use the Segment Addition Postulate to write an expression for the total length. We will add the lengths AB and BC.
b We know the total length of PR and the length of the first segment, PQ. We need to figure out an expression for the second partial segment length, QR.
Since all the points are on a straight line, we can form an equation for the total length. The Segment Addition Postulate tells us that the total length PR is the sum of PQ and QR.
