Measurement Length and Perimeter - Perimeter of Rectilinear Shapes - Planning

In a Year 4 mathematics lesson focused on the perimeter of rectilinear shapes, students advance their understanding of perimeter by calculating the lengths of missing sides without the use of squared paper. The lesson employs a variety of resources, including worksheets and a presentation, to guide students through the process of finding perimeters using addition and subtraction. Key vocabulary such as 'centimetres', 'metres', 'equivalence', 'perimeter', 'lengths', 'add', and 'subtract' are central to the lesson, with vocabulary cards available for reinforcement. The class begins with a recap of previous learning and a starter question that prompts students to recognise and discuss rectilinear shapes, comparing them to shapes studied in earlier lessons. Through partner talk and class discussions, students explore how to deduce the measurements of unlabelled sides using known lengths and the concept of equivalence. For example, if one side of a shape is composed of two lengths that add up to 10cm, and the opposite side is missing, students learn to calculate that missing length and, subsequently, the entire perimeter of the shape.

The lesson encourages collaborative learning, with partners working together to identify missing lengths and calculate perimeters of various rectilinear shapes. Key questions guide students to consider the importance of opposite sides and how to use part-whole models to find missing lengths. To address common misconceptions, the lesson places emphasis on careful calculation when using equivalence to find missing sides. The plenary includes a 'Give me five' reflective activity, where students consider what they've learned, the skills they've used, and what they found challenging. Differentiated activities are provided to cater to varying levels of understanding, from working towards finding one missing length in centimetres, to working at expected levels where children find trickier missing lengths, and up to greater depth where students deal with multiple missing lengths and measurements in both centimetres and millimetres. This structured approach ensures that all students are supported in mastering the concept of perimeter in rectilinear shapes.