Check up 2 was about identifying the similar shapes by finding the scale factor. Every similar shape has a scale factor. A scale factor is the number multiplied by one corresponding side to get the other corresponding side. If you multiply the original perimeter by the scale factor you will get the new perimeter. You can also find the scale factor by dividing the corresponding sides by each other. I did just that to find the scale factor, if there was one, in each shape.