Calculate the side length of a regular polygon by division where the perimeter is known

Maths

Know that a regular polygon has sides that are the same length and angles that are the same size

Know that the perimeter is the distance around a 2D shape

Understand that different shapes can have the same perimeter

Know that perimeter is measured in units of length and can be found by counting or measuring units

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

Know that the perimeter of a rectangle can be calculated by addition and multiplication

Know that unknown side lengths can be calculated from the perimeter and known side lengths

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

Solve problems involving the perimeter and side lengths of polygons

In this unit pupil will learn perimeter as the distance around the edge of a 2D shape. They will learn perimeter is measured in units of length found by counting units and by calculating by adding the side lengths of a 2D shape. In the future unit pupils will pupils will complete and compose symmetrical shapes from two congruent shapes and investigate lines of symmetry in 2D shapes. 

In the prior unit pupils investigated ways to compose and decompose polygons. They investigated quadrilaterals with and without parallel and perpendicular sides. In this unit pupil will learn perimeter as the distance around the edge of a 2D shape. They will learn perimeter is measured in units of length found by counting units and by calculating by adding the side lengths of a 2D shape.

In this unit pupil will learn perimeter as the distance around the edge of a 2D shape. They will learn perimeter is measured in units of length found by counting units and by calculating by adding the side lengths of a 2D shape.

Perimeter

Divide the number of sides by the perimeter.  

Divide the perimeter by the number of sides.

If you know the perimeter of a regular polygon, what can you do to find the length of each side?

What is the side length of a square with a perimeter of 16 cm? 

Lucas has measured the perimeter of his classroom, which is square-shaped. Its perimeter is 24 metres. What is the length of one side of the classroom? {{ }} m.

What is the side length of a regular triangle with a perimeter of 15 cm? {{  }} cm.

What is the side length of a regular five-sided shape with a perimeter of 30 cm? {{  }} cm

What is the side length of a regular five-sided shape with a perimeter of 300 cm? {{  }} cm.

What is the perimeter of a square with a side length of 5 cm? {{  }} cm.

What is the perimeter of a regular triangle with a side length of 5 cm? {{  }} cm.

What is the perimeter of a regular pentagon with a side length of 5 cm? {{  }} cm.

Lucas is trying to work out 20 ÷ 5 but he is struggling. How else might he think of this question?

A regular triangle with a side length of 5 cm 

A regular pentagon with a side length of 4 cm

Order these shapes from smallest perimeter to longest.

Calculate the side length of a regular polygon by division where the perimeter is known

Lesson outcome