Any two polygons are similar if their corresponding angles are
congruent and the measures of their corresponding sides are
proportional:
In the figure above the ratio or the scale factor of the
quadrilateral to the left versus the quadrilateral to the right is
½. We could also turn it around and say that the scale factor for
the quadrilateral to the right to the quadrilateral to the left is
2.
Video lesson: Find the ratio between the two
similar figures