Answer:
2.5
Step-by-step explanation:
From the diagram, figure B was enlarged to obtain figure A.
The two figures are therefore similar.
The corresponding sides are in the same proportion. That constant value of the proportion is called scale factor.
It is given by:
[tex]k = \frac{image \: length}{corresponding\:object \: length} [/tex]
Figure B is the image of A
[tex]k = \frac{10}{4} = \frac{25}{10} = \frac{21.5}{8.6} = 2.5[/tex]
Therefore the scale factor is 2.5
