I'm assuming you don't know the definition of similarity, which is fine, but I want to clarify just in case you don't: Similarity is when two figures are the same in angles ONLY, and their sizes are proportional. Given this, PQR has a side 20" and TUV's respective side is 6". Now, there's a ratio: 20:6 Now, would you agree that it would then be logical that the perimeter would follow the same ratio? Where 60:P(TUV)? Hope this helps some!