Perimeter; Area of Rectangle (Part - 3) - Perimeter and Area, Mathematics, CBSE Class 7 Video Lecture

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let us move on to a rectangle so how do
we find the perimeter of a rectangle so
that's again pretty simple because again
when we talk about perimeter we are
concerned only about the boundary so
perimeter is the total length of
boundary now in rectangle what happens
now
length of all the sides are not equal so
let's say if this side if the length is
L then the opposite sides are equal but
what about the break so breadth will be
different let's say it is B then again
the opposite sides will be equal so this
would be P so perimeter would be the
total length of the boundary that is L
plus B plus L plus B that is sum of all
the four sides so this is equal to n
plus L would be two L similarly B plus B
would be 2 B so 2 n plus 2 B so 2 would
be common so this would be L into B so
the perimeter of rectangle would be 2
into length plus bread now what about
area of a rectangle so the concept here
would remain the same as was in a square
so in case of square it was side into
side because both the sides both the
edges and sides would equal in length
now in this case that is not the case so
in this case if this side is L then this
side is B so in this case the area would
be length into breadth that is as I had
mentioned before so you consider this
rectangle to be made up of lines each of
length L and then you you stack many
such lines one above another to form the
rectangle so basically you are
multiplying L be number of times or you
are adding L so you are adding 1 one
line of length L how many times be
number of times so that is basically
length into breadth therefore the area
of rectangle
is given by length into brick so in case
of rectangle also the unit of area would
be meter square or centimeter square
depending on whether the length of the
side is given in meter or centimeter
now you might wonder that if I do we
need to find the area or perimeter of
squares or rectangles for that matter
now
in the very first slide in the
introduction slide I had already told
you some examples where you want to
carpet the floor of your room all you
want to laminate the road or do you want
to fence a rectangular field now in each
of these pieces you need to know the
area and perimeter without that you just
can't do so what do we do now let us
look at some problems for our day-to-day
life so we will look at actual problems
with measurements and we will try to
solve them using the concepts of area
and perimeter question number one the
perimeter of a rectangular sheet is 100
centimeters if the length is 35
centimeters find it spread also find the
area so basically here you have a
rectangular sheet so the moment you have
rectangular sheet obviously all the
sides would not be equal only opposite
sides would be equal so here it is said
that the perimeter is given as 100
centimeters now what do we know what is
the perimeter of a rectangle so
perimeter is equal to 2 into length plus
breadth so this parameter is given as
100 centimeter now
length of the rectangle is also given as
35 centimeters so we have to find out
the breadth and we also need to find out
area so now if you look at this equation
here 2 into length plus breadth is given
as 100 now in the question length is
already given as 35 so this is 35 plus V
is equal to 100 so let us assume that
breadth is B so therefore 2 into 35
be 70 plus 2 into B is 2 B is equal to
hundred or we can say 2 B is equal to
hundred minus 70 so hundred minus 70 is
30 therefore B is equal to 30 divided by
2 so 2 into 15 is 30 so breath will be
equal to 15 centimeter so this is the
breadth of the rectangular sheet
now what about area so we again know
that area is nothing but length into
breadth so length is 35 and breadth is
15 so 35 into 15 is 525 centimeter
square so this would be the area thank
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