Geoboard to create the shapes Students will create a rectangle with a perimeter of 10 (or 12, or another amount). How many different ways are there? Be cautious with diagonal connections because they are not equivalent to vertical or horizontal connections. Think of how you can get students to discover this without just telling them. Initially, students will count the squares inside the shape. Students need more efficient ways to figure this out (multiplying, decomposing into smaller sections, etc.). This app is also great for creating irregular shapes which students may decompose into smaller rectangles or triangles. Then check them with the standard formulas.