A solid is composed of a cylinder with hemispherical ends.

Solution:

Height of the cylinder = height of entire solid - height of sphere 1 - height of sphere 2
= 108 - 18 - 18

= 108 − 36

= 72 cm

r = 18 cm

C.S.A. of cylinder

$=2 \pi \mathrm{rh}$

$=2 \pi \times 18 \times 72$

 

$=8138.88 \mathrm{~cm}^{2}$

C.S.A. of 2 hemispheres = surface area of a sphere

$=4 \pi r^{2}$

$=4 \pi(18)^{2}$

$=4069.44 \mathrm{~cm}^{2}$

Surface area of solid

$=8138.88+4069.44$

 

$=12208.32 \mathrm{~cm}^{2}$

Cost of polishing $1 \mathrm{~cm}^{2}=7$ paise $=0.07 \mathrm{Rs}$

Total cost

$=12208.32 \times 0.07$

 

$=$ Rs $854.58$