In triangle ABC, D, E, and F are the midpoints of BC, CA, and AB, respectively. A dilation maps A to D, B to E, and C to F. What is the scale factor of this dilation?

In a median, DG:DA = 1:3, where G is the centroid. So the scale factor is 1/3.

Why are you asking this question a second time? You already asked it in the previous question. I answered it the first time, look there to see.