Question

In a building there are 24 cylindrical pillars. The radius of each pillar is 28 cm and height is 4 m. Find the

cost of painting the curved surface of all pillars at the rate of rupees 8 per​

Answer 1

Answer:

• Radius of pillar (r) = 28 cm = 0.28 m
• Height of pillar (h) = 4 m
• Find cost of painting CSA of 24 pillars if rate is Rs. 8 per m²

• Curved Surface Area of 1 Pillar :

⇒ CSA = 2πrh

⇒ CSA = 2 × 22/7 × 0.28 m × 4 m

⇒ CSA = 2 × 22 × 0.04 × 4 m²

⇒ CSA = 7.04 m²

• Cost of Painting of 24 Pillars :

⇢ Cost = 24 Pillars CSA × Rate

⇢ Cost = 24 × 7.04 × 8

⇢ Cost = Rs. 1351.68

∴ Cost of painting the pillars is Rs. 1351.68.

Answer 2

Given:

• number of pillers in the building = 24
• radius of each of the piller = 28cm
• height of the pillars = 4m

To Find:

cost of painting the curved surface of all pillars at the rate of ₹8 per m²

Solution:

• radius = 28cm = 0.28 m

we know that:

${ \boxed{ \sf{ \purple {\: curved \: surface \: area \: of \: cylinder \: = 2\pi rh}}}}$

So,

$\sf{curved\: surface\:area\:of\:each\:pillar}$

$\implies\sf{2 × \frac{22}{7} × 0.28 × 4}$

$\implies\sf{\frac{49.28}{7}}$

$\implies\sf{7.04m²}$

Now,

surface area of 24 pillars

$\implies\sf{7.04 × 24m²}$

$\implies\sf{168.96m²}$

it is given that:

cost of cleaning per metre square = 8

so,

cost of painting 24 pillars

$\implies\sf{₹168.96 × 8}$

$\implies\sf{₹1351.68}$

Hence,

cost of painting the curved surface area of all the pillars is ₹1351.68

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☆Formulae Related To Cylinder ☆

⊱ Area of Base and Top = πr²

⊱ Curved surface area = 2πrh

⊱ Total surface area = 2πr(h + r)

⊱ Volume = πr²h