Answer:
The scale factor is 1.
Explanation:
Let k be the scale factor of a dilation of triangle ABC to form the image triangle A'B'C'.
The dilation is a magnification if

In this case, the preimage will be similar to the image triangle.
If

the dilation is a reduction. The image and pre-image will still be similar.
But if

the image is the same as the preimage.
We say the pre-image is congruent to the image triangle.