This Interactive Smartboard lesson allows students to move a transparent tablecloth over a table in order to more clearly understnad how extended dimensions are found. It is a big eye opener when students can actually determine where the numbers come from and how to derive the missing values. The same is done with a frame. Students can move a frame over a picture in order to find the missing dimensions as well as the width of the border around the frame. The activity extends to assist students in finding the area of a shaded region (area of the frame) Perimeter can be incorporated if you desire.