Measure and calculate the perimeter of composite rectilinear shapes in centimetres and metres - Reasoning

When exploring the concept of measuring and calculating the perimeter of composite rectilinear shapes, students are encouraged to think critically and apply their reasoning skills. Composite rectilinear shapes are figures that consist of multiple rectangles or squares joined together, and understanding how to work with these shapes involves recognising the total distance around the outside of the shape, which is known as the perimeter. To calculate the perimeter, students must measure the length of each individual side in centimetres or metres, taking care to only include the outer sides that form the boundary of the entire shape.

Reasoning activities in this area challenge students to go beyond simple calculations by presenting problems that require a deeper understanding of the properties of shapes and the concept of perimeter. For instance, students may be asked to find missing side lengths given the total perimeter, or to compare the perimeters of different shapes to determine which one is longer. These activities help to develop problem-solving skills and the ability to logically explain the process and the reasoning behind their answers. It's important for students to recognise that in composite rectilinear shapes, some sides may be shared between the rectangles or squares, and therefore, they should not be counted twice when calculating the total perimeter.