In KS2 Maths children will come to understand both perimeter and area. In Year Four children will learn how to work out the perimeter of a square or a rectangle and how to calculate the length of the sides in a square from its perimeter. They will also be introduced to the correct units to use (mm^{2} cm^{2} or m^{2}) when measuring area and asked to make realistic estimates of a shape's area.

When measuring a 2D shape, like a square or a rectangle, it is useful to know what the perimeter and area of a shape are. The perimeter is the total distance around the outside of a two-dimensional shape. Area is the amount of space covered by the shape's surface. To work out the area of a rectangle multiply the length of its longest side by the length of its shortest side. This will give you an answer in square mm, cm or m (mm^{2} cm^{2} or m^{2}).

Take this quiz for 8-9 year olds to discover what you know about area and perimeter.

1.

Which is a good estimate of the perimeter of a mobile 'phone?

100cm

34cm

2m

25mm

100cm = 1m That's way too big for a 'phone!

2.

What is useful to work out the area of a small 2D shape?

Tracing paper

Measuring jug

Metre stick

Squared paper

Squared paper helps to work out the area of irregular shapes too

3.

Which would be a good estimate of the area of a small notebook?

1,000cm^{2}

5cm^{2}

26cm^{2}

500cm^{2}

This would be a very small notebook measuring 4cm x 6.5cm

4.

What is area?

The distance around the edge of a 2D shape

The distance across a 2D shape

The size of the surface of a 2D shape

The distance around the edge of a 3D shape

Area is measured in square mm cm m or km

5.

What is the perimeter of a rectangle 5cm x 9cm?

14cm

20cm

28cm

45cm

A rectangle has two sides of equal length and two more side with equal length. So the answer is:

(2 x 5) + (2 x 9) which is

10 + 18 = 28

(2 x 5) + (2 x 9) which is

10 + 18 = 28

6.

A square has a perimeter of 32cm. How long are the sides?

4cm

8cm

10cm

16cm

As a square has four equal sides, we divide by 4 to get the answer

7.

What is a perimeter?

The distance around the edge of a shape

The distance across a shape

The size of the surface of a 2D shape

The size of the surface of a 3D shape

To calculate the perimeter of a 2D shape, add together the length of each side

8.

What is the perimeter of a 6cm square?

6cm

12cm

18cm

24cm

A square has four equal sides, therefore the perimeter will be 4 x 6 = 24

9.

Which would be a suitable unit to measure the area of a classroom?

Square metres

Square millimetres

Square centimetres

Square kilograms

Millimetres and centimetres would be way too small and kilograms measure weight!

10.

How is square centimetre usually written?

Cm sq

Sq cm

cm^{2}

Cubed cm are written as cm^{3}