Transcript Area of Shapes - Every Maths Topic

Area of Shapes
 The area of a shape is the space it occupies.
 Try guessing the name of these shapes first:
Parallelogram
Trapezium
Square
Rectangle
Triangle
Circle
The Square
Area = l x b
b
l
e.g. Find the area of a square of
side 3.5 cm.
A = l x b Discuss
and work out
A = 3.5this
cm example
x 3.5 cm
together
= with
12.25your
cm2 friend.
The Rectangle
Area = l x b
b
l
e.g. Find the area of a rectangle of
length 3.5 cm and height 80 mm.
Since units must be the same:
10 mm = 1Discuss
cm
80 mm and
= 80work
mm ÷out
10 = 8 cm
this example
A = l x b together.
A = 3.5 cm x 8 cm
= 28 cm2
The Parallellogram
Area = b x h
e.g. Find the area of a parallelogram
correct to 1 d.p.
h
height
3.8 cm
10.3 cm
b
base
A = b Discuss
xh
A =and
10.3
cm out
x 3.8 cm
work
=this
39.14
cm2
example
= 39.1
cm2
together.
h
b
The Triangle
Area = ½ b h
e.g. Find the area of triangle ABC
correct to the nearest cm2.
A
h
height
b
base
4 cm
B
11.7 cm
A = ½b
xh
Discuss
A =and
½ work
x 4 cmout
x 11.7 cm
h
=this
23.4
cm2
example
b
= 23
cm2
together.
½ area
Area
Area of
of parallelogram
= ½b
 h of= parallelogram
bh
C
The Trapezium
Area = ½h(a + b)
e.g. Find the area of the trapezium.
Length aof side a
8.5 cm
height
h
6 cm
Length bof side b
a
h
12 cm
b
h = 6cm, a = 8.5 cm, b = 12 cm
A about
= ½h(athe
+ b)
Decide
values
A = ½ x 6 of
cma,xb(8.5
andcm
h + 12 cm)
= ½ x to
6 cm
findx the
20.5area.
cm
a
b
= 61.5 cm2
Area
Rotate
Copy
Area
of2 of
1the
trapeziums
the
trapezium
parallelogram
trapezium
trapezium
form
is=half
parallelogram
h(a+ +b)b)
The
trapezium
½ a=h(a
The Circle
Area = p r2
Radius
r
Centre
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.
Find the radius first
2
A =and
p rthen
work out
example
= pthis
x 9.5
cm x 9.5 cm
together.
= 283.5
cm2
= 284 cm2