Surface Area of Cube and Cuboid (Part - 2) - Surface Area and Volumes,

hello friends this video on surface area
and volume is part two is brought to you
by exam Viacom no more fear from exam
let's understand you what before that it
understand the concept of Len read in
height this is the carnations if you
have a cuboid given to the straight line
that is almost perpendicular to your
x-axis this will be height okay line
along x-axis is considered to be length
and the other line is considered to be
red
please note this is convention sometimes
the questions there don't give what is
length for the spread for the side or
they don't give the orientation but they
give the values and you have to figure
out as per the convention which is the
correct way okay because of you should
know my ass is mine different based on
which orientation do you solve the
question what do understand is the this
is the convention I have seen so by
default this H value X will be length
valid 2 y will be height and the
remaining one will be right ok so now we
have to find the surface in your the
cuboid this is cuboid occupied a busy
told that it has a six age of six
surface one two three four five six nine
one two three four five six so that is Q
body it has six are different surface
and if you see it has one two three four
and one two three four eight and then
again before it has twelve edges so it
has let me write twelve edges six
surface okay that is Q boy
and these are perpendicular to each
other not be able to find the surface
area of the cuboid that means for
example this is a box this is the cuboid
box and I want to know how much paper is
required to make this hollow cube widen
I was using this horribly way I want to
know that so let's find how to find the
surface any of the q''-word
to find is what we can do is let's break
this q1 so let's move this first surface
up let's move the second service down
right and yeah so if you see here a or
let's do one thing let's give a
carnations first so so if you see this
side is let's suppose this Len and he'll
make it B this is B this is height let
these be the dimensions of the cuboid
ABC okay or I can say it will be a sled
making its making a he'll be a jelly
this is this is this will fight okay now
let's move the first rectangle out so
this side is L and this side is B
correct
let's move the seconds also down this
side is l and this side is B let me this
direction so in the city you seen this
is hell this is H it if see this is a
similarly this one this is B and this is
H let's move other one as well so here
also it is B and this is H yeah next
move this as well so L and this height
was H
so we have got these six figures okay
okay so now we have got what we've got
six of tangles and now to find the
surface via area we have to just find
the area of these rectangles and hat
and let me number then this be one two
three four five and six
so let me write total surface area of
the cuboid it will be what will be your
1 plus a view of 2 if you have three
area for 5 minute of 6 correct so let's
add this area of 1 is what length into
bread here you have to use what length
into I hear you have trees what breath
in to hide in your four is one length
into bread in your 5 is what length into
hide area of 6 is one breath it should
be see lb is common twice so I would say
twice and B elegy is also common twice
plus twice avenged and VH is also twice
twice pH so if you take two commonly
this lv+
allege Plus that is the surface area of
this cube I will not do always be just
and we have done months and will use the
same form log in okay
note that for cuboid there is a
different type of surface in here that
is called lateral surface in here you
something and laggards our vision is not
equal to e2 length plus
I okay so when you say laterals
Abyssinia we don't take the top and the
bottom so length and do breath is not
taking you see L into B is missing this
part is visible if you don't take this
part so what you get is a cuboid I mean
you just get AB lateral surface of
either of the cuboid so when I say
laterals are busy they are it will be
once again natural surface area I am
saying ignore this part ignore this area
and ignore the below areas you take only
this area the same here this here the
end the idea blue so ignore the top and
bottom what you get is a lateral surface
area okay and that's fine lot of surface
area is 2 into L plus B into H because
this is length and this is red so L into
B twice of L into B is ignored that is
the top and the bottom the cuboid is
node so let's try to find a surface area
of the cube now so inserting Q we know
that all the sides are of length a right
so one option is we know the idea of
cuboid where it is cuboid as 2 into L
into B plus LS plus BH so one thing is
you can just put L is going to be equal
to H is equal to a L into become V
becomes a 2 a n into H becomes a into a
and B into H also becomes a into E and
this becomes if you saw already become
6a squared so that is one way of solving
it all it's the same thing again so we
have six we have cuboid with six sides
all sides same length break this Jewboy
okay bring this qy into 6 piece and you
will notice that all these sites which
we have God has dimension K into it all
this way all this are nothing but
squares so you are seeing in this way
because and as
orientation but actually these are
squares with the area but it is in into
it right now for this U of 1 square is
what e square similarly we have one two
three four five six square so 6 into e
square is 6 e square so the area of
cuboid will be sufficient you of the
cuboid will be 6 in square right
goodnight so let me lay surface easy-off
cuboid will be what 6 e square similarly
the lateral surface area we need no but
the lateral surface area of so it is Q
of Q billabong for a square Y because
the top and the bottom is ignored we
have only four squares area to we are
okay let's understand concepts of suffix
P and Q when cuboid with some simple
numerical okay and then tell you what
talking to seeing the bushes
first as you should see always the
dimensions it should be the same
sometimes this may be centimeter this
midterms we have to all convert all
these in to see Mero okay and then you
have to check what on area they are
looking for it let's start with the
question so Mary wants to decorate her
Christmas tree she wants to place the
tree on a wooden box covered with
colored people with the pictures of
Santa Claus and there may be some Santa
Claus pictures on this okay this box
which is covered with the paper which
has Santa Claus pictures on it
she must know the exact quantity of
people to buy for this purpose you want
to cover this with piece of paper and he
must you want to one know what is a how
much people is required for this purpose
and the length breadth and the height of
the box is given how many square sheet
of paper of this side would be required
correct
so for that see once you want to cover
the whole of this box which you see with
people and this is a cuboid box length
bed and height are given so first we
have to find surface area of what would
in most surveys in your the wooden box
we have just seen his word is nothing
but two into length breadth + vh correct
and luckily the dimensions are all in
saying the red so nothing to worry so
put the values here so this becomes 2
into L into P that is e 2 into 40 plus B
into H 14 to 20 plus L into H that is 18
to 20 and this is centimeter square so
better put number here L be in H so you
know what is L what is V what is that
you okay so you saw this this becomes 2
into 8 18 to 40 is 3 to double 0 14 to
20 is 880 into 20 is 1600 a tenth is a
centimeter square so you saw this
renounce to mean to 5600 centimeter
Square and it is nothing but 1 1 to
double 0 centimeter square so this is
the surface area of this box but
the question didn't ask for it the
question says is that Mary has to cover
this right and to cover this she need
this many centimeter square of people
but the question is harmony square
sheets of paper she required so square
sheet of people each of the square shape
dimension is given right so surface area
of square sheet is 140 into 40 and
luckily that is also in centimeter
centimeter square so the number of she
referred would be what number of seats
required what service area of wooden box
by surface in your sheet you saw this
one one two double zero centimeter
square by this is 1600 centimeter square
by 1600 centimeter square cancel and you
saw that comes out to be seven so seven
sheets are required and that is the
answer so what we did here we found the
surface area of the box we found the
surface area of the shield and then we
could actually find the number of
shields required to cover this box okay
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