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

Starter quiz

Match the numbers so that they sum to 10
- 7
  
  ⇔
  
  3 ✓
- 5
  
  ⇔
  
  5 ✓
- 4
  
  ⇔
  
  6 ✓
- 2
  
  ⇔
  
  8 ✓
Complete: 4 + 3 + 4 + 3 = ______
- '14' ✓
Match the unit of measure to the correct abbreviation.
- millimetre
  
  ⇔
  
  mm ✓
- centimetre
  
  ⇔
  
  cm ✓
- metre
  
  ⇔
  
  m ✓
- kilometre
  
  ⇔
  
  km ✓
16 + 8 = ______
- '24' ✓
This shape has a perimeter of ______ units.
- '6' ✓
What is the perimeter of this shape?______ units.
- '14' ✓

Exit quiz

Which calculations could be used to work out the perimeter of the number shape?
- 3 + 2
- 2 + 3 + 2 + 3 ✓
- 3 + 3 + 2 + 2 ✓
- 3 + 2 + 3 + 2 ✓
- 3 + 2 + 3 + 2 + 3
Use adding to find the perimeter of the shape. The perimeter is ______ units.
- '12' ✓
Laura says the perimeter of this shape is 6 units. What mistake do you think she has made?
- Counted one side twice.
- Not counted all of the sides. ✓
- Counted the squares inside the shape.
What is the perimeter of this shape? ______ units.
- '19' ✓
Which of these statements is true?
- There is not enough information to work out the perimeter of this rectangle.
- You can work out the perimeter of the rectangle by calculating 4 + 5 + 4 + 5 ✓
- You can work out the perimeter of the rectangle by calculating 5 + 5 + 4 + 4 ✓
What is the perimeter of this square? ______ units.
- '12' ✓

Worksheet

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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.