4.2 Area

Mathematics

Perimeter, area and volume

Educator section

Memorandum

a)

(i) 9

(ii) 13

(iii) 16

b)

(i) 9 cm

(ii) 13 cm

(iii) 16 cm

• area of square = length x 4

8.

a) 28 m; 45 m ²

b) 6 cm

c) 4 km; 24 km

d) 7 cm; 28 cm ²

e) 11 m; 11 m

9.2

a) 15 000; 1.5

b) 37 500; 3,75

c) 24 000; 2,4

9.3

a) 15 000 000; 15

b) 9 000 000; 9

c) 37 500 000; 37,5

Leaner section

Content

Activity: area [lo 4.2, lo 2.5, lo 2.3]

6. AREA

6.1 IMPORTANT to KNOW!

The area of a figure is the size of the flat surface that is included within the outside boundary of a figure. If you sweep your hand over this whole page, you have touched the whole surface of the page. If you paint a wall, we call the amount of space you have painted, the area.

6.2 Also IMPORTANT to REMEMBER:

Area is expressed in square units, e.g. square centimetre (cm2) or square metres (m2).

6.3 Memorise the following:

1 cm² = 10 mm x 10 mm = 100 mm²

1 m² = 100 cm x 100 cm = 10 000 cm²

1 km² = 1 000 m x 1 000 m = 1 000 000 m²

6.4 Ask your educator to photostat the following page or trace it just as it is:

a) Cut out the small squares and see how many of them will fit in the following figures.

__________________________________

__________________________________

__________________________________

b) What is the area of :

figure (i)? __________________________________

figure (ii)? _________________________________

figure (iii)? _________________________________

6.5.1 There is a quicker way to find out the area of figures!

We can use formulas,

e.g. rectangle

= length x breadth

= 5 x 2

= 10 cm2

6.5.2 Can you write down a formula that will determine the area of a square?

_____________________________________________________________________

7. Can you draw two different rectangles, each having an area of 48 cm²?

8. Work together with a friend and complete the following table:

9.1 Did you know?

The area of farms is calculated in hectares (ha).

1 ha = 100 m x 100 m

= 10 000 m²

9.2 Use your calculator and complete the following table:

9.3 Complete the following with the help of your calculator:

Assessment

Learning Outcome 4: The learner will be able to use appropriate measuring units, instruments and formulae in a variety of contexts.

Assessment Standard 4.2: We know this when the learner solves problems;

Learning Outcome 2: The learner will be able to recognise, describe and represent patterns and relationships, as well as to solve problems using algebraic language and skills.

Assessment Standard 2.3: We know this when the learner represents and uses relationships between variables in order to determine input and/or output values in a variety of ways.

Assessment Standard 2.5: We know this when the learner solves or completes number sentences by inspection or by trial-and-improvement, checking the solutions by substitution (e.g. 2 x - 8 = 4).