Examples: Surface Area of Cube and Cuboid Video Lecture - Class 9

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question say is that Hawaii he has meant
a cubicle water dam you see is the
cubicle water tank that he has built it
has a lid so that means top is there
talked is there should we see a
particular avoid has excites and in some
question we have seen the leaders not
there so we take care of only five sites
in this the lid is there and with each
outer 1.5 meter so each case is 1.5
meter this is a cube so all the sides
are 1.5 meter and this lid has to be
taken care he gets down to such as of
the time excluding the base that means
the base is not there so we have 4 plus
1 5 sides so five sides of you we will
do okay because the base is not applied
or it has to be covered with curve
square dial has to be covered with
square lights and he side is 25
centimeter please note this is meters
once meter or the centimeter so let's
convert everything in centimeter to be
on seaside so 1.5 meter is nothing but
150 centimeters cause this is gonna keep
on every centimeter so as we keep we
need this may be a right here 130
centimeter this is this edge and each of
these square tiles
it is 25 centimeter is 20
why okay so we have to find the total
cost for the tiles at the cost for part
doesn't that is part well piece 360 is
the cost so before finding the total
cost we have to find the number of tiles
required to cover the whole tank this is
the time time it's like even this is a
cubical tank and only five sites has to
be covered so there's already one things
to be noticed in this question one is
the units are different second is this
cubical furnace the lid has to be taken
here the base should not be are taken
care so there are five sides to the spy
sides
he should have we should apply some
training and thinking to come up with
five sides and then once you have come
up with a number of places where then
part doesn't cost is given partners and
cost will find the cost of one right and
then you can find the total cost
so let's first find the surface area of
the tank to find the number of tires
required so surface area to be covered
right or to be tail is 5 B square in the
side because each side is a square and
then 5 sides 5 a square and you put the
bellows become centimeter square this is
the surface area of time to be covered
okay now let's find the service any of
the tines or any other dance here time
is here as we needed two-dimensional we
can depth we are not considering it
the square tiles and please no square
dance become 25 be a square I don't let
me say sides well there's nothing to say
but even and the sign is 25 so I was 25
into 25 becomes the square so what is
the number of I see quite long time is
required we do what surface area to be
tiny pellets never covered details by
area of each 10 to the minus 5 into 150
into is the centimeter square and this
is 25 into 25 is also centimeter square
it's cancel and you saw this you get 180
times and that's so 180 times are
required now we have to find the
customer so cost of 12 times is how much
360 what does it therefore cost of 180
days will be how much 3 60 by 12 that is
cost of one time into one integrates
cost of 180 type container it is into
piece put the value okay so this becomes
15 360 you comes out to be 5 this is the
total cost required for tiling this
particular
cubical water tank and 5 side please pay
attention in this question there so many
concepts to learn here first thing is
the units are in different they're
different units
some are admittance
be understanding this question we have
to come out we have to understand that
five sides of this cubicle Bank has to
cover then it has to be covered with
square tiles dimensions are given way to
find the number of tiles once you find
the number of tiles you divide the cost
to find the cost also they have not
given the cost of world is given the
cost of but doesn't I hate to be that
you have to first find the cost of one
tile and then you have to find the cost
of one eighty type okay a plastic box
1.5 meter long 1.5 meter wide 65
centimeter deep so if you see here it's
not that is to be made okay
it is to be open and the top the top is
not there only five science they also
let me write five science
now let me write these concepts here by
you say it's not easy okay ignoring the
thickness of the plastic sheet they
remind the area required for making this
box so we'll assume that the plastic
sheet has no thickness we defined the
area of the she's required to make this
box and you have to hard to find the
cost of the sheet of the cost of one
square meter that's given so you see
most of the units are in meters so let's
convert this also inhibitor so point
sixty five hundred millimeter point six
five and sixty five centimeters of the
1.65 meters okay so I just made
everything in middle so one part is
resolved
now you see now here you understand
which is length which is white and which
is
so we know that African nation this side
is lent this is bread and this is light
and this will be used here because one
side is missing in this is a cuboid you
should and it is mentioned that the top
has missing you see top this busy so
what will be the dimension at the top to
know that you should know the convention
so length is 1.5 meters and the height
is 0.65 okay so now since the top is
missing so we have to find the surface
area surface area open top will be what
so you see we have to find the area of
all these five edges if you see this is
what length into height so they are two
lengths in two by two lengths in Dubai
correct this side and this similarly the
set was bred into white so this side and
the same one to bred into what about the
bottom part whatever I do you see it
will be lengthy to read only one so
looking at this drawing in this drawing
the figure first write the conventions
then only we could actually come up with
this form that's very very important
these great ancient hair types and how
oh my god has values first we do you
plastic box with our top and then we
assigned
values 1.5 1.5 0.6 5 me the dimensions
we have a sign please on the conventions
because we know that that this side is
length the side is bread and the same is
height so with that and we know that
this is the top is open that is the
length and width 1 LM doing this
particular rectangular piece is missing
to know that we have to first create
this else she will not know which corner
to use right so you may say give us L
into h plus 2 bh + 2 lv because one side
has to be missing but it is not the case
it is mentioned at the top this is so
what are the dimension at the top that
is L into me to know this dimension we
have to do all the surface ok so once we
have this formula we'll put the values
of the small hard to come up the surface
area there is 2 into L into B 1 point 5
into 1 point 2 5 into 5 plus 2 into B
into mesh so L into H 1 point 5 to point
6 5 2 into B into H this one point two
five into point six five plus telling to
be ready to be one point five into one
point two five and all in victor so it
becomes meter square okay so you saw
this this becomes one point nine five
this becomes one point six two five this
is 1 point 8 7 5 meter square and you
saw all this further you get five point
four five meter square so that is the
surface area of this open top box later
or box open in the top first part is
done any of the sheet required is this
now e to find the cost so it is mention
that one meter square cost of one meter
square is what
20 so cost of 5.45 meter square the
reward 5.45 endo 20 you saw this you get
one zero nine hundred nine two pieces
required to create this box okay thank
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