Teaching and Group Activities for Understanding
Day 1 Teaching
Draw right-angled triangles and discuss how to find their areas by considering each as half of a rectangle. Demonstrate that this works for any triangle. Conclude area = half base × height.
-- Find the areas of rectangles and then divide these to find the areas of triangles.
-- Generalise how to find the area of right-angled triangles. Test with other types of triangle.
Day 2 Teaching
Show a set of quadrilaterals and identify parallelograms. Demonstrate how to find the area by dividing into 2 triangles and a rectangle. Find areas and derive formula after the activity.
-- Derive a formula for finding the area of a parallelogram.
Day 3 Teaching
Revise finding areas and perimeters of rectilinear shapes. Show some shapes with the same perimeter. Demonstrate that these have different areas. Can you approximate the area of a bedroom floor? The area of a village? The surface area of a little finger nail? One side of a sticky note?
Use the in-depth problem-solving investigation ‘Through the window’ from NRICH as today’s group activity.
Or, use this activity:
-- Use investigative strategies to find the dimensions of a rectangle of specified area. Investigate compound shapes.