Area

CBC Grade 5 Mathematics — Area

Lesson Objectives

By the end of this topic, a learner should be able to:

• Identify the square centimetre as a unit for measuring area
• Work out the area of rectangles and squares
• Appreciate the use of area in everyday situations

Area

Area is the flat space inside a shape. It tells you how much surface something covers.

a) The square centimetre

We measure area in square centimetres, written cm².

One square centimetre is a square measuring 1 cm on every side.

Picture covering a shape with these little squares and counting them. That count is the area.

b) Counting squares

Draw a rectangle on squared paper, 7 squares long and 4 squares wide.

Count them one by one and you get 28.

Counting works, but it is slow. There is a quicker way.

c) Area of a rectangle

Instead of counting every square, count one row and how many rows there are.

There are 7 squares in a row, and 4 rows. So 7 × 4 = 28.

The rule is area = length × width.

Both measurements must be in the same unit. You cannot multiply centimetres by metres.

d) Area of a square

A square has all four sides the same length.

So the rule is area = side × side.

A square of side 6 cm has an area of 36 cm².

e) Square units, every time

Area answers always end in cm² or m², never plain cm or m.

The small 2 is not decoration. It says the answer counts squares, not lengths.

If your answer has no small 2, you have found a length instead.

f) Area is not perimeter

Perimeter is the distance all the way round the edge. It is a length, measured in cm.

Area is the space inside. It is measured in cm².

A rectangle 7 cm by 4 cm has a perimeter of 22 cm. Its area is 28 cm². The two numbers answer different questions.

g) Where this is used

Working out how many tiles cover a floor. Buying cloth for a table. Finding how much paint a wall needs. Measuring a garden plot.

:::checkpoint Check yourself

1. What does one square centimetre look like?
2. Find the area of a rectangle 9 cm long and 5 cm wide.
3. Find the area of a square of side 8 cm.
4. What is the difference between area and perimeter? :::

Definitions

• Area — the amount of flat surface a shape covers.
• Square centimetre (cm²) — a square measuring 1cm by 1cm.

Must Remember

1. Area of a rectangle = length x width; area of a square = side x side.
2. Always include cm² in the answer.
3. Make sure both measurements are in the same unit before multiplying.

Conclusion

Every area calculation for a rectangle or square comes down to multiplying two side lengths.