Description: Lindsay finds missing side lengths on polygons when given all other side lengths and the perimeter. Created by Lindsay Spears. So we're told this figure down here has a perimeter of 24 centimeters. But what we want to know is what is the length of the missing side? So we've got to figure out what number should go on this missing side so that the entire length is 24 centimeters.*Teacher Advisor is 100% free.