Answer:Scale factor = 1/2
The purple shape is a dilation of the black shape.
A dilation is a transformation that produces an image that is the same shape as the original, but is a different size.
Now findd the scale factor.
If given two shapes and need to find the scale factor, We must know which one was the original and which one is the image or the new shape. Then we need to know the length of corresponding sides and set them up in a ratio like so: Scale Factor = purple/black
Scale factor = 10/20 = 1/2