The end point of a line segment PQ is against 4 cm mark and the end-point Q is against the mark indicating 14.8 cm on a ruler. What is the length of the segment PQ?

Now we have to extend the line segment QP towards point 0 of the ruler and take a point 0 on the line QP which is extended corresponding to point 0 on the ruler.

From the diagram we know that,

OP = 4 cm

OQ = 14.8 cm

It can be written as,

PQ = OQ – OP = (14.8 – 4) cm = 10.8 cm