Given:
The point is B(2,5) and its image is B'(1,2.5).
To find:
The scale factor.
Solution:
If a figure is dilated by the scale factor k and (0,0) is the center of then the scale factor is defined as
[tex]k=\dfrac{\text{x-coordinate of the point on image}}{\text{x-coordinate of the corresponding point on the original figure}}[/tex]
x-coordinate of point B' is 1 and the x-coordinate of point B is 2. So, the scale factor is
[tex]k=\dfrac{1}{2}[/tex]
Therefore, the scale factor is [tex]\dfrac{1}{2}[/tex] and the correct option is D.