Know that unknown side lengths can be calculated from the perimeter and known side lengths
I can calculate unknown side lengths of rectangles from the perimeter and known side lengths.
Know that unknown side lengths can be calculated from the perimeter and known side lengths
I can calculate unknown side lengths of rectangles from the perimeter and known side lengths.
These resources will be removed by end of Summer Term 2025.
Lesson details
Key learning points
- Subtraction and halving can be used to calculate the missing side length of a rectangle.
- If you know the perimeter and one of the side lengths you can subtract the known sides and halve the difference.
- Mental and written methods can be used to calculate the perimeter of a 2D shape.
Keywords
Perimeter - The distance around a two-dimensional shape.
Common misconception
Pupils may see a rectangle with the perimeter given and only one of the side lengths and think that there is insufficient information as there are three missing side lengths.
Remind pupils that because it is a rectangle, the side length opposite the given side length is in fact known. A counter can be added on and then removed again to show that they actually know two of the missing side lengths, not just one.
To help you plan your year 4 maths lesson on: Know that unknown side lengths can be calculated from the perimeter and known side lengths, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your year 4 maths lesson on: Know that unknown side lengths can be calculated from the perimeter and known side lengths, 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.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 2 maths lessons from the Perimeter unit, dive into the full secondary maths curriculum, or learn more about lesson planning.
Licence
Starter quiz
6 Questions





Exit quiz
6 Questions


