M3.6.5 For the adult
Trapeziums and joined shapes
How do I find the area of a flower bed with two parallel sides of different lengths?
What this chapter teaches
Two copies of a trapezium make a parallelogram, so the area of a trapezium is half of (the parallel sides added) × the height. A shape made of rectangles and triangles is split into parts, and the areas are added, or a missing corner is taken away.
Three questions to ask
There is no one right wording. Listen for the idea.
- How can you make a parallelogram from two trapeziums?
- A trapezium has parallel sides of 8 cm and 4 cm and a height of 5 cm. What is its area?
- How could you find the area of a house end shaped like a rectangle with a triangle on top?
After the chapter, the learner can
- Find the area of a trapezium
- Find the area of a shape made of rectangles and triangles
What they copy into their notebook
Trapezium: add the two parallel sides, multiply by the height, then halve. Joined shape: split it into rectangles and triangles and add. Or take a missing corner away.