To determine the magnitude of dilation used to create triangle A′B′C′ from triangle ABC, you will need the coordinates of the corresponding points of the triangles or the lengths of the sides before and after dilation.
The formula for the magnitude of dilation (k) from triangle ABC to triangle A′B′C′ is given by:
\[ k = \frac{\text{length of side of triangle A′B′C′}}{\text{length of corresponding side of triangle ABC}} \]
If you can provide the lengths of a corresponding side of triangles ABC and A′B′C′ or their coordinates, I can help you calculate the dilation factor. Otherwise, without the specific image or values, it's impossible to determine the magnitude of dilation. Please provide further information!