Finding a length in composite shapes
I can solve area problems of composite shapes involving whole and/or part circles where the area is known and the radius or diameter must be found.
Finding a length in composite shapes
I can solve area problems of composite shapes involving whole and/or part circles where the area is known and the radius or diameter must be found.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- The diameter can be found from the area of circles or parts of circles by rearranging the formula.
- The radius can be found from the area of circles or parts of circles.
- The diameter or radius can be found from the area of composite shapes by reasoning and rearranging the formula.
Keywords
Sector - A sector is the region formed between two radii and their connecting arc.
Diameter - The diameter of a circle is any line segment that starts and ends on the edge of the circle and passes through the centre of the circle.
Radius - The radius is any line segment that joins the centre of a circle to its edge.
Common misconception
If I want to find the radius of a semicircle from its area, I half the area first.
You must double the area. This calculates the area of a full circle, whose radius can be found by first dividing by π, then square rooting.
To help you plan your year 8 maths lesson on: Finding a length in composite shapes, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 8 maths lesson on: Finding a length in composite shapes, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
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Explore more key stage 3 maths lessons from the Perimeter, area and volume unit, dive into the full secondary maths curriculum, or learn more about lesson planning.
Licence
Starter quiz
6 Questions
Exit quiz
6 Questions



