Examples: Perimeter and Area of Square and Rectangle Video Lecture - Class 7

hello friends this video on perimeter
and area part 4 is brought to you by
example comm normal fear from exam
question number 2 the area of a square
part is the same as of a rectangular
part so basically there are two parks
one is in the shape of a square and the
other one is in the shape of a rectangle
and the problems is that the area of the
square part and the area of the
rectangular park are the same okay if
the side of the square part is 60 meters
that means the length of each side is 60
meters and the length of the rectangular
part is 90 meters as that is these
lengths are 90 meters find the breadth
of the rectangular part so you need to
find out the breadth or the width of the
rectangular part okay so what would be
the area of a square of the square pack
so we know that area of a square is
equal to side into side right and what
is the area of a rectangle so the area
of the rectangular part would be length
into breadth now as per the question
area of the rectangular part is equal to
the area of the square part so length
into breadth is equal to side to side so
length in case of the rectangle is given
as 90 breadth is something that we need
to find and side of the square is given
as 60 so this would be 16 to 60 so B
will be equal to 60 into 60 divided by
90 so here it would be 3 3 so 9 3 2 6 3
to 6 0 so this is equal to 40 meters
therefore the breadth of the rectangular
part would be 40 meters question number
3 a door of length 2 meters and breadth
1 meter is fitted in a wall so here as
you see this is the wall
and this is that daughter so what are
the dimensions of the doll the length of
the door is two meters and the breadth
is one meter okay the length of the wall
is 4.5 meters and the breadth is 3.6 so
that means this length of the wall is
4.5 meters and the breadth is 3.6 okay
find the cost of whitewashing the wall
if the rate of whitewashing the wall is
rupees 20 per meter square now when you
have to whitewash the wall how much
region of the wall needs to be
whitewashed do you think that the entire
area of the wall needs to be whitewashed
not really because when you find out the
area of the wall that is the area of
this rectangle in that case you are also
including the door but the door will not
be whitewashed right we do not wash the
door so all the region except the door
needs to be whitewash so for that what
we need to do we need to find out the
area of first you find out the area of
the wall width door that is including
the area of the door so what would be
the total area it is a rectangle right
so the total area would be length into
breadth that is four point five into
three point six so four point five into
three point six is sixteen point two
meter square so this is the total area
of this rectangular one now let us find
out the area of the doors now the door
is also in the shape of a rectangle so
this would also be length into breadth
that is 2 into 1 which is equal to 2
meter square so this is the area of the
door now we have to find out area of the
wall to be by it washed because we are
not going to whitewash the door
therefore the area of the wall to be
white washed will be
do the total area - the area of the door
so sixteen point two minus two meter
square which is equal to fourteen point
two meter square so this is the area of
the wall which needs to be whitewashed
now we have to find out the cost of
whitewashing so it says that the rate is
rupees twenty per meter square that
means cost for whitewashing one meter
square is rupees twenty therefore the
cost for whitewashing fourteen point two
meter square would be how much fourteen
point two into twenty so fourteen point
two into twenty would be 284 so to piece
284 would be the cost of whitewashing
this one so I hope you understood the
concept right because when we want to
whitewash the wall will be only one to
know this area that is the area of the
wall excluding the door so what we did
is we first find out the entire area of
the wall with door then we found out the
area of the door and then we subtracted
the area of the door to find out area of
the one to be by it washed thank you
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