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.

How is square centimetre usually written?

Cm sq

Sq cm

cm^{2}

Cubed cm are written as cm^{3}

3.

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

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 6cm square?

6cm

12cm

18cm

24cm

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

6.

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

7.

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

8.

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!

9.

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

10.

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