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- Surface Areas and Volumes - Exercise 13.1
- Surface Areas and Volumes - Exercise 13.2
- Surface Areas and Volumes - Exercise 13.3
- Surface Areas and Volumes - Exercise 13.4
- Surface Areas and Volumes - Exercise 13.5
- Surface Areas and Volumes - Exercise 13.6
- Surface Areas and Volumes - Exercise 13.7
- Surface Areas and Volumes - Exercise 13.8
- Surface Areas and Volumes - Exercise 13.9

Question 8 Surface Areas and Volumes - Exercise 13.3

A bus stop is barricaded from the remaining part of the road, by using 50 hollow cones

made of recycled cardboard. Each cone has a base diameter of 40 cm and a height of 1 m. If the

outer side of each of the cones is to be painted and the cost of painting is Rs. 12 per \mathbf{m}^{2}

what will be the cost of painting all these cones? (Use π = 3.14 and take √(1.04) = 1.02)

Answer:

Given:

Radius of cone, r = diameter/2 = 40/2 cm = 20 cm = 0.2 m

Height of cone, h = 1 m

= (1.04)

Or l = 1.02

The slant height of the cone is 1.02 m

Now,

CSA of each cone = πrl

= (3.14 x 0.2 x 1.02)

= 0.64056

CSA of 50 such cones = (50 x 0.64056) = 32.028

CSA of 50 such cones =

32.028 \mathrm{m}^{2}

"hello students welcome to lito q a video
session
i am saf your math tutor and question
for today is
a bus stop is barricaded from the
remaining part of the road
by using 50 hollow phones made of
recycled cardboard
each phone has a base diameter of 40
centimeter
and height 1 meter if the outer
side of each of the cone is to be
painted and the cost of painting is
rupees 12 per meter square
what will be the cost of painting all
these cones use pi
is equal to 3.14 and take root of 1.04
is equal to 1.02
let us see what is given given is the
diameter
that is 40 centimeter
hence radius
r can be given as 40 upon 2
half of the diameter is radius so 20
centimeter which can be written as 0.2
meter
height is given 1 meter
and slant height is not given so let us
say slant height of the cone
l and l will be equal to
root of h square plus
r square so root of
1 square plus
0.2 square and that is root of
1.04 in the question
value of 1 root of 1.04 is 1.02
so our slant height is root
of one point zero four that is one point
zero two meter
once you found the slant height you can
easily found curve surface area of
cone so curl surface area that is c
as a of one cone
that will be equal to pi into r into l
pi value has to be taken as 3.14
radius 0.2
and slant height l that is 1.02
so this is the slant height l
and here current surface area
that is csa
comes out to be for one cone it is
0.64056
unit is meter square
now we can write it like this that
current surface area of one cone is
zero point six four zero five six meter
square
so what will be the curved surface area
of 50 such cones because there are 50
holophones
and that will be equal to 0.64056
into 50 and that is
32.028
meter square this is for the 50
such cones now it is given that the cost
of painting is rupees 12 per meter
square
so for one meter square area
cost is rupees 12
so how much will be the cost of 32.028
meter square area
so for 32.028 meter square
area your
the cost will be 12 multiplied by
32.028
and that is rupees 384 point
three three six
rupees will be your cost this is the
approximate
cost that is 384
point three four that is approximate
in rupees therefore we can write our
statement in conclusion that
the cost of painting all these cones
that is 50 cones
is rupees 384.34
so it is our final answer if you have
any query you can drop it in our comment
section
and subscribe to ledo for more such q a
thank you for watching
"

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