Answer: Locate two corresponding ordered pairs of the two shapes. Calculate how much the pre-image values were multiplied by to obtain the image values. This is your scale factor. You can calculate this by dividing the coordinates of the mage by the corresponding coordinates of the pre-image.
Find the distance between two points on the original figure. Find the distance between the corresponding points on the transformed figure. The scale factor is the ratio of the latter distance to the former one.
_____ If you know the center of dilation is the origin, you can simply divide any non-zero coordinate of the transformed figure by the corresponding coordinate of the original figure to get the scale factor.
