Know that perimeter can be calculated by adding together the side lengths of a 2D shape

I can calculate the perimeter of a 2D shape by adding together the lengths of the sides.

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Year 4

Know that perimeter can be calculated by adding together the side lengths of a 2D shape

I can calculate the perimeter of a 2D shape by adding together the lengths of the sides.

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Share activities with pupils

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Lesson details

Key learning points

Perimeter is the sum of the side lengths of a 2D shape.
If you measure the side lengths you can add them to calculate the perimeter.
Mental and written methods can be used to calculate the perimeter of a 2D shape.

Common misconception

Pupils may believe that there is only one way to add the perimeter of a shape - typically clockwise, starting from the top. This is untrue and will limit the efficiency of the arithmetic.

The lesson presents the idea of the side lengths being given in counters. The counters can then be re-ordered, for example so that a number bond to ten can be utilised. Using counters or sticky notes or similar may support pupils.

Keywords

Perimeter - The distance around a two-dimensional shape.

This lesson uses fluency in addition and pupils should be secure in number bonds within 20 and summing single digits mentally. Consider how you may revisit these key facts prior to the lesson or provide a scaffold for less fluent learners.

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Licence

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