New
New
Year 4

Understand that the perimeter of a regular polygon can be calculated by multiplication

I can calculate the perimeter of a regular polygon using multiplication.

New
New
Year 4

Understand that the perimeter of a regular polygon can be calculated by multiplication

I can calculate the perimeter of a regular polygon using multiplication.

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Lesson details

Key learning points

  1. If you know the length of one side of a regular polygon you can calculate the perimeter.
  2. Multiply the side length by the number of sides of the regular polygon to calculate the perimeter.

Keywords

  • Perimeter - The distance around a two-dimensional shape.

  • Regular - A regular polygon has all sides equal and all angles equal.

Common misconception

Pupils may overgeneralise and assume all perimeters can be calculated by multiplying one side length by the number of sides in the polygon.

'Noticing' is a key mathematical skill. Encourage pupils to take their time to notice whether the shape is regular or irregular, if that information is not already explicitly given.

Pupils will revisit multiplication tables learned in Years 2 and 3 within this lesson. Fluent recall will allow for pupils to focus on the concept. Consider providing multiplication grids for pupils who are less confident.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
Which of these describe this shape?
An image in a quiz
Correct answer: irregular polygon
regular polygon
not a polygon
Q2.
What is the perimeter of this rectangle?
An image in a quiz
12 units
17 units
Correct answer: 24 units
Q3.
Select all of the regular polygons.
Correct answer: a
b
Correct answer: c
d
Q4.
Select all of the squares.
a
Correct answer: b
Correct answer: c
d
Q5.
Which of these red lines shows the perimeter of the triangle?
a
Correct answer: b
c
d
Q6.
Match the shape to the correct number of sides.
Correct Answer:triangle ,3

3

Correct Answer:square ,4

4

Correct Answer:pentagon ,5

5

Correct Answer:hexagon ,6

6

Correct Answer:octagon,8

8

6 Questions

Q1.
What is the perimeter of a square with a side length of 4 cm? cm.
Correct Answer: 16
Q2.
What is the perimeter of a regular triangle with a side length of 4 cm? cm.
Correct Answer: 12
Q3.
What is the perimeter of a regular pentagon with a side length of 4 cm? cm.
Correct Answer: 20
Q4.
What is the perimeter of a regular octagon with a side length of 4 cm? cm.
Correct Answer: 32
Q5.
Order these shapes from smallest perimeter to longest.
1 - A square with a side length of 3 cm
2 - A regular triangle with a side length of 5 cm
3 - A regular pentagon with a side length of 4 cm
Q6.
Which of these shapes will have the same perimeter as each other?
Correct answer: A regular triangle with a side length of 6 cm
A square with a side length of 4 cm
A regular pentagon with a side length of 3 cm
Correct answer: A regular hexagon with a side length of 3 cm