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Perimeter Year 3

Teach your Year 3 class about perimeter with this ready-to-teach Maths lesson. Your class will explore what the word ‘perimeter’ means before looking at how to calculate the perimeter of rectilinear shapes. Starting with counting squares, they can then progress to measuring shapes and calculating the perimeter from the length and width of the shapes.

This perimeter Year 3 Maths lesson includes:

  • a detailed lesson plan with differentiated activities
  • a slideshow for the teaching input
  • a range of printable resources for independent learning activities
  • answer sheets where necessary

This lesson is part of a 2D Shape Maths scheme of work for Year 3.

Perimeter Year 3 Lesson Pack

£2.99

Scroll through the pictures for a preview of the lesson's resources:

Perimeter Year 3 slideshow example 1
Perimeter Year 3 slideshow example 2
Perimeter Year 3 slideshow example 3
Perimeter Year 3 slideshow example 4
Perimeter Year 3 slideshow example 5
Perimeter Year 3 slideshow example 6
Perimeter Year 3 worksheet example 1
Perimeter Year 3 worksheet example 2
Perimeter Year 3 lesson plan example 1
Hands holidng a tape measure

Perimeter

What is perimeter?

The perimeter is the total length around the outside of a 2D shape.

How to work out perimeter

To find the perimeter of a 2D shape, you need to add up the lengths of all the sides.

Working out the perimeters of a triangle, square, rectangle and pentagon

Working out the perimeters of a triangle, square, rectangle and pentagon.

The perimeter of a rectangle

Because the opposite sides of a rectangle are equal in length, to work out the perimeter we only need to know the measurement of the length and the width of the shape. We can write the perimeter of the rectangle as twice the sum of its length and width.

Formula for the perimeter of a rectangle

Perimeter of a rectangle = length + length + width + width

We can write this as:

P = l + l + w + w

This can be simplified to:

P = 2(l + w) 

Using the formula to work out the perimeter of a rectangle

Using the formula to work out the perimeter of a rectangle

 

The perimeter of a square

Because all of the sides of a square are equal in length, to work out the perimeter we only need to know the measurement of one of the sides. We can write the perimeter of the square as four times the length of one side.

Formula for the perimeter of a square

Perimeter of a square = length + length + length + length

We can write this as:

P = l + l + l + l

This can be simplified to:

P = 4l  

Using the formula to work out the perimeter of a square

Using the formula to work out the perimeter of a square

 

When should children learn about perimeter?

According to the National Curriculum Maths objectives, children start to learn about perimeter in KS2. It is assigned as compulsory learning under the 'Measurement' strand of learning.

In Year 3, children should learn to:

  • measure the perimeter of simple shapes

In Year 4, children should learn to:

  • measure and calculate the perimeter of a rectilinear figure (including squares) in centimetres and metres

In Year 5, children should learn to:

  • measure and calculate the perimeter of composite rectilinear shapes and centimetres and metres

In Year 6, children should learn to:

  • recognise that shapes with the same areas can have different perimeters and vice versa