


How can we
classify
different shapes?
Closed
figures are figures
which when drawn starts and
ends at the same point.
Some
examples are square,
circle, rectangle etc.
Open
figures are the
figures which when drawn
will start and end at
different points.
A
B
 Perimeter is the length
of the boundary around
a closed figure.
Hey, can you
guys find the
perimeter of
my land ?
 Suppandi’s
plot’s perimeter= 11+12+11+12
= 46 c.m
 Let
us now find the
perimeter of this
figure:
as,
perimeter is the sum of all sides
of a shape,
Here: perimeter = 4c.m+4c.m+8c.m+8c.m
= 24 c.m
II wonder if there is
any easy method to
find the perimeter
of a rectangle, like
of a chess board.
 From
this example we can see that
perimeter of
rectangle is equal
to twice the sum
of its length and
bredth.
so,
Perimeter of rectangle= length+length+
bredth+bredth
= 2 length+ 2 bredth
=2 (l+b)
So finding the perimeter
of square will also be
easy because we only
have to double the
length of one side of the
square. Isn’t it?
Yeah it might
be so!!!!! but
I am not sure.
 PERIMETER
OF SQUARE
When length of one side of square= 4 c.m
= 4+4+4+4
= 2(4+4)
=4 x side
“Dudes, she does not
know how to find the
perimeter of an
equilateral triangle. I
hope you know??? ”
To find the perimeter of an equilateral triangle
we just have to add all the 3 sides of it, or as
the equilateral triangle have all its sides equal
we can multiply the length of side by 3.
Perimeter of equilateral triangle
= 3 x length of one side.
EQUILATERAL
TRIANGLE
Area
is the total surface
present inside a figure.
Area’s
unit is (m2)
I wonder what is the formula
for finding the area of a
rectangle?
I will ask Hermione.
Area of a rectangle =
length x breadth
 Area
 Here
of a rectangle = length x breadth
if,
length of rectangle=4 c.m and if
breadth of rectangle=5 c.m then
area of rectangle= 4x5 = 20 c.m2
Will someone tell me
the formula to find the
area of a square?
I don’t know how to
find the area of one
side of a dice, which is
a square.
Area
of a square = side x side.
Here area of square
= side x side
= 5c.m x 5c.m
= 25c.m2
Do you know how to find
the area of a triangle?
Such as a side of a
pyramid.

Area of a triangle = 1 breadth x height
2
Here, if breadth = 2c.m
and height = 2c.m then,
area = 1 x 2 x 2
2
= 2 c.m2
 Regular
shapes have all its sides of equal
length and all its angles of equal magnitude.
My garden is a
square plot, can I
call it as a regular
rectangle?
Yes, my silly old bear
because if a rectangle
have all its sides and
angles equal then it
will become a square.
Q1.)
 Ans:
So guys can you
tell me the area of
a triangle with
breadth 8 c.m and
height 4 c.m?
16
Area of triangle= 1 x 8 x 4
2
= 1 x 32
2
= 16c.m2
Q2.)
Tell me the formula
for finding the area
of a triangle?
Ans: area of a triangle = 1 x breadth x height
2
Find the height of
a triangle of area
6 and breadth 2?
 Q3.)
Ans:6 c.m
area of a triangle= 1 x b x h
2
height= area x 2 = 6 x 2
b
2
= 6 c.m
Can you tell me,
what is meant by
regular shapes?
Q4.)
Ans: Regular shapes have all sides
equal and all angles also equal.
 Q5.)
 Ans:
Hey could you tell
us the area of a
square with one
side=12 c.m?
Area of square = side x side
= 12 x 12
= 144c.m2
 Q6.)
Tell me if I can
call a rectangle
as a regular
square.
No, it is not
possible.
 Ans:
No, it is not possible to call a rectangle
as a regular square because a regular square
will have all its sides and angles equal and it
is not a rectangle. But a regular rectangle
can be called as a square.
 Q7.)
Are there figures like
regular Hexagon?
 Ans:
There are figures like regular Hexagon
because a hexagon which has all its sides and
angles equal are known as a regular shape.
 Q8.)
Find the perimeter
of the following
figure?
 Ans:
Perimeter = 2+5+4+1+4+5+2+5+4+1+4+5
= 42 c.m
 Q9.)
Can you guys tell me
the exact area of a
triangle with base
12.5 c.m and height
10 c.m?
 Ans:
Area of triangle = 1 x b x h
2
= 1 x 12.5 x 10
2
= 125 = 62.5 c.m2
2
I know how
to do it.
 Q10.)
 Ans:
Hey can you tell me
the number of presents
I have if it is the same
number as the length
of a rectangle with
area 26 and breadth 2?
Area of rectangle= length x breadth = 26
26= length x 2
length = 26
2
= 13
Santa has 13 presents with him
All figures can be divided into two as open and
closed figure.
 Perimeter is the sum of all sides of the boundary
of a figure.
 Perimeter of rectangle = 2(l+b)
 Perimeter of square = 4 x side
 Perimeter of equilateral triangle = 3 x side
 Area is the amount of surface present inside a
figure.
 Area of rectangle = length x breadth
 Area of square = side x side.
 Area of triangle = 1 x b x h
2
Regular shapes have all its sides and angles equal
