CK-12 Foundation
Ck 12: Elem Math: Perimeter in Grid
[Free Registration/Login may be required to access all resource tools.] Students watch a video and attempt practice problems on how to find the perimeter of a shape using a grid.
Khan Academy
Khan Academy: Area and Perimeter on the Coordinate Plane
Find the area and perimeter of quadrilaterals using their coordinates. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video or receive hints.
University of Georgia
University of Georgia: Texas Area Estimate
Drawings and discussion of several methods to estimate the area of an irregular shape, like the state of Texas.