Perimeter and Area - Area of Irregular Shapes - Planning

In a Year 5 lesson on the topic of Measurement focusing on Area and Perimeter, students delve into the concept of calculating the area of irregular shapes. The lesson begins with a starter activity to refresh their understanding of counting squares to estimate areas. The children are then presented with an irregular shape on a square grid, where they learn that unlike rectilinear shapes, irregular shapes do not have a straightforward formula for calculating area. They are taught to approximate the area by counting whole squares within the shape and combining part-squares to form additional whole squares. This method is practiced with Tia's example, which includes 6 whole squares and 12 parts, and the children learn how to systematically annotate the shape to avoid repetition. They then compare the areas of three different irregular shapes, discussing which has the greatest area and why, considering the scale of the grid.

During the plenary, the children consolidate their understanding of how to find the approximate area of an irregular shape, using the method of counting and combining squares. They are encouraged to annotate their work to keep track of their counting. The lesson extends the concept to different square sizes, where children learn to adjust their area calculations by multiplying the original estimate by the new area of the squares. For example, if each square represents 1m², 2m², or 3m², the area of the shape is recalculated accordingly. The lesson also includes group work, where children create a 'Pirate Island' map, applying their knowledge of area to meet specific criteria. They exchange maps with other groups to verify if the criteria have been met. Key questions and common misconceptions are addressed to ensure a deep understanding of the topic, with differentiated worksheets provided for independent learning. The lesson structure aims to guide students from working towards fluency to achieving greater depth in their understanding and application of the concept.