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Area - Revision
The area of a shape is simply defined by :
“the amount of space a shape takes up.”
Think of a square measuring 1 cm by 1cm we say it is :
1cm
1cm
1cm2
( 1 square centimetre )
Area of a Rectangle
Example
Find the area of the rectangle
L = 9cm
B = 2cm
Area = Length x BreadthA = L x BA = 9 x 2
A = 18 cm2
Area of a Rectangle
Example
Find the length B of the rectangle opposite
L = 12cm
B cm
Area = Length x Breadth
A = L x B
36 = 12 x B
Balancing Method
A = 36cm2
36B =
12
B = 3cmRemember
units
Calculate the area of this shape
8cm
9cm
5cm
6cm
A = l x b
A = 9 x 8
A = 72cm2
A = l x b
A = 6 x 5
A = 30cm2
Total Area =
= 102cm2
72 + 30
Area of a Composite
Calculate the area of this shape
5cm
6cm
16cm
5cm
A = l x b
A = 16 x 5
A = 80cm2
Rectangle 1
Rectangle 2
A = l x b
A = 6 x 5
A = 30cm2
Total Area = 80 + 30
=110cm2
Area of a Composite
7
Any Triangle Area
2
18 6
224
Area
Area cm
6cm
8cm
Example 1 : Find the area of the triangle.
12
Area b h
Any Triangle Area
14 10
2Area
10cm
4cm
Example 2 : Find the area of the triangle.
12
Area b hAltitude h outside triangle this time.
220Area cm
Parallelogram AreaExample 1 : Find the area of parallelogram.
Parallelogram Area b h Area = 9 3
2Area = 27cm9cm
3cm
Area of a Rhombus
1Rhombus Area= (D×d)
2
D
d
Rectangle Area = (D×d)
This part ofthe rhombus
is half of the smallrectangle.
Area of a Kite
1Kite Area= (D×d)
2
D
d
Rectangle Area = (D×d)
Exactly the same process as the rhombus
Rhombus and Kite Area
1Rhombus Area= (D×d)
21
Area = (5×2)2
Example 1 : Find the area of the shapes.
5cm
2cm
2Area = 5cm
1Kite Area= (D×d)
21
Area = (9×4)2
2Area = 18cm
9cm
4cm
Trapezium Area
1Area 1 = a×
2h 1
Area 2 = b×2
h
1 1Total Area = a× b×
2+
2h h
W
X Y
Z
1
2
a cm
b cm
h cm
Two triangles WXY and WYZ
1Trapezium Area = (a+b)
2h
Trapezium Area
1Trapezium Area = (5+6)×4
2
1Trapezium Area = (a+b)
2h
Example 1 : Find the area of the trapezium.
6cm
4cm
5cm
2Trapezium Area = 22cm
Parts of the Circle
Circumference
O
O = centre of circle
The radius is measured fromthe centre of the circle
to the edge.
radius
diameter
The diameter is measured from one edge to the other
passing through the centre of the circle.Radius = ½ x diameter
Diameter = 2 x radius
Main part of a Circle
10cm
2cm
C D2D r 4D cm
Example : Find the length of the circumference (Perimeter) of each circle
C D 10
31.4 cm 4
12.56 cm
Area of a circle
Q. The diameter of the circle is 60cm. Find area of the circle?
Solution
2A r60
302 2
D
r cm
230A22826 A cm