Examples: Volume of Cuboid and Cube Video Lecture - Class 9

hello friends in this video on surface
area and volume sparked 16 is brought to
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example ok let's take one more question
find the cost of digging a cuboidal pit
you are taking a cuboidal bit and
dimensions of the Potocki when 8 meter
long length speed meter long 6 meter rod
and the 3 meter need all units and the
rate is given 30 rupees permit review
pretty easy so you just find the volume
of this pit right if you get the book
and this is the stand
just try to understand why not to find
surface area wide to find volume because
the cost of digging is given per meter
cube that means we are looking for
volume right that is also one end so
first we find the volume of pit that is
length into breadth into height so this
guy is supposed to take this pit so that
is 8 into 6 into 3 meter cube that is
the volume of return you solve it you
get 144 meter cube so cost of digging
one meter cube is what group is 30 so
cost of doing 144 meter cube will be
what rupees 30 into 144 and that does
nothing but rupees for 3 to 0 okay
pretty easy so you are expected to dug a
pit and when you dig a pit it is all
involved in because you could take out
some volume or swell now each of the
rates will be in the wall
okay so if you are expected to dig a bit
then in this kind of scenarios you are
talking in the terms of volume because
you have to take out soil to
the big okay up alleged having a
population of 4,000 they requires 150
liters of water per head per day and
their 4,000 people staying in the
village it has a time of this how many
days the one in the last so if it has a
population of 4,000 and requires 150
liters of water per day so per day
consumption of water is one of what
weighs what number of people Hindu 150
liters and that will mean liters that
comes out to be yeah it is actually six
lakh litres that is the consumption per
day and the pertinent time is a meter is
the time the village the time dimension
for a meter so it can be converted into
meters yes we can so we know that 1000
liters will do one so with that we can
convert this by dividing this by
so what unit is 600 so the party
consumption is 600 meter okay what is it
that capacity tank a person is nothing
but the calling all the time only what
life is nothing but length into breadth
away and there is nothing but 20 into 15
into 6 and that is nothing but 1,800 so
partaken container 600 rip you tank
capacity is equal to how many days it
will last so days it will last
it's not the part that kept acidity
consumption that is nothing but 600
handsome three days and that is the
answer it easy see theory for example if
you have two breads and you feel it one
bread per day how many days it will last
obviously two days eight one day H
similarly if you have 1800 meter cube of
water and you need 600 meter cube of
water per day to last three days or you
just make in this fashion if you have
eighteen hundred rupees and daily if you
need 600 rupees then in three days your
money will get exhausted same concept
a solid cube of sight 12 centimeters is
a cube of size 12 centimeter all 12
let's cut into a cube of equal volumes
you've got eight cubes of equal volumes
what will be the side of YouTube then
what will the ratio between their
surfacing see you two cut into equal
this is my own applies of brain to think
you have to cut this into eight cubes to
cut this into eight cubes a good way is
to cut in this direction so you cut in
this direction if you cut in this
direction you'll notice that you'll get
one two three four five six seven and
there is one cube behind so you get 8
loops right this is all one resolve one
three or so we have one two three four
five this is all same six seven and
there is one cube behind so this is the
way you can cut so if this side was to L
and this is equal card this side will be
six and the side will be 6 so new cube H
will be six right so side of your cube
is 6 centimeter what is the ratio of
this have you seen u sub P serious
so service area of cube large surface
area of Q small Q blood surface against
what six nine six six a square six into
a large square and this is the six into
a small square this one is cancel a
large is what 12 a small is what six and
two
that becomes fooled by one so that does
not ratio of their areas if you want to
find the ratio of their volumes that is
not given but asked but let's find the
ratio of their volumes also so volume of
Q large by volume of Q small is nothing
but a large cube by a small cube the
values 12 6 Q so the ratio of their
volume is 8 by 1 the ratio of their area
is 4 by 1 and the ratio of their side is
likely to buy one okay a river that is 3
meter deep this is the river this river
the last point okay this is 3 meter deep
and 40 meter wide this is our even this
will be hosted 40 meter wide and there's
a depth you can't see here this is
flowing at the rate of 2 kilo meter per
hour and how much water is fall into the
sea a minute if it is a meter here and
it is the reclamators we had to first
come up with a meter unit here so that
this is to limit or I can make it as
2000 meter per hour how much water will
fall into see you know in a minute
h1 are a 60 minute 60 minutes it flows
2000 meter so 1 minute
how much to flow 2000 by 60 meter that
is nothing but 100 by 3 so that is this
is hundred by three so visualize this as
a cuboid where 100 by 3 meter is the
length 40 is the width and 3 is the
height and this full of water because
this much water will actually flow into
sea
the question is that this is the river
water does the river and it is going in
to see this river is 3 meter deep 40
meter wide and it has a length length we
don't know why because the deeper water
is flowing the water is flowing at the
speed of 2000 meter per hour that is 100
by 3 meter per minute so in one minute
100 by 3 meter actually flows right so
this is a cuboid which has 100 by 3
meter as a length 40 meter as the wet
and 3 meters height okay so volume of
this Q point is is equal to L into B
into H put the values hundred by 3 into
14 to 3 this is meter cube cancel so
this 4000 meter to 4000 meter cube of
water will actually fall into C so this
question is more about this variety if
you visualize properly that if the river
has 3 meter deporting interwined and it
has some rate of flowing so with that
rate of flowing you can find the length
of water that flows per minute that
becomes a length of the cuboid and the
width and the height is already given
and with that you can actually find the
volume of the cuboid the volume of the
keyboard is nothing but the volume of
water that will flow from river to see
in that particular time duration thank
you
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