area of shapes n the area of a shape is the space it occupies. n write down the name of each shape....
TRANSCRIPT
Area of Shapes The area of a shape is the space it occupies. Write down the name of each shape.
Square
Rectangle
Parallelogram Trapezium
CircleTriangle
A powerpoint presentation by
Carmelo Ellul Head of Department (Mathematics)
Area of Shapes Click button to select topic.
SquareRectangleParallelogram
TrapeziumTriangle
CircleEnd Show
The Square Area = l x b
b
e.g. Find the area of a square of side 3.5 cm.
Discuss and work outthis example
together with your friend.
A = l x b
A = 3.5 cm x 3.5 cm
= 12.25 cm2
llength
breadth
The Rectangle Area = l x b
l
b
e.g. Find the area of a rectangle of length 3.5 cm and height 80 mm.
Discuss and work outthis example
together.
Since units must be the same:10 mm = 1 cm80 mm = 80 mm ÷ 10 = 8 cm
A = l x bA = 3.5 cm x 8 cm
= 28 cm2
The Parallellogram Area = b x h
baseb
heighth
b
h
e.g. Find the area of a parallelogram correct to 1 d.p.
3.8 cm
10.3 cm
Discuss and work outthis example
together.
A = b x hA = 10.3 cm x 3.8 cm
= 39.14 cm2
= 39.1 cm2
The Triangle Area = ½ b h e.g. Find the area of triangle ABC
correct to the nearest cm2.
Discuss and work outthis example
together.
A = ½b x hA = ½ x 4 cm x 11.7 cm
= 23.4 cm2
= 23 cm2
baseb
heighth
Area of parallelogram = b hb
h
Area of = ½ area of parallelogram b
h
11.7 cm
4 cm
A
B C
Area of = ½b h b
h
b Area of trapezium = ½ h(a + b)Rotate the trapeziumThe 2 trapeziums form a parallelogram Area of parallelogram = h(a + b) Area of 1 trapezium is half h(a + b)
Area = ½h(a + b)a
b
h
h
a
e.g. Find the area of the trapezium.
12 cm
8.5 cm
6 cm
Decide about the values of a, b and h
to find the area.
h = 6cm, a = 8.5 cm, b = 12 cm
A = ½h(a + b)
A = ½ x 6 cm x (8.5 cm + 12 cm)= ½ x 6 cm x 20.5 cm = 61.5 cm2
The Trapezium
Length of side a
Length of side b
Copy the trapeziuma
b
height
The Circle Area = r2
CentreRadiusr
Remember: the radius
of a circle is half the diameter.
e.g. The diameter of a circle is 19 cm. Find, correct to nearest whole number, the area of a circle.
Find the radius first and then work out
this example together.
r = 19 cm ÷ 2= 9.5 cm.
A = r2
= x 9.5 cm x 9.5 cm= 283.5 cm2
= 284 cm2
The Circle Area = r2
r
Remember: the radius
of a circle is half the diameter.
e.g. The diameter of a circle is 19 cm. Find, correct to nearest whole number, the area of a circle.
r = 19 cm ÷ 2= 9.5 cm.
A = r2
= x 9.5 cm x 9.5 cm= 283.5 cm2
= 284 cm2
End Show