Question

In a building there are 18 cylindrical pillars. The radius of each pillar is 21cm and height is 4m. Find the total cist of painting the curved surface are of all pillars at the rate of rupees 7 per m²​

Answer 1

Given data : In a building there are 18 cylindrical pillars. The radius of each pillar is 21 cm and height is 4 m.

To find : The total cost of painting the curved surface area of all pillars at the rate of Rs 7 per m².

Solution : Now, we need to convert radius of pillar, centimetre to meter.

⟹ 21 cm = 21/100 = 0.21 m

Hence, radius of cylindrical pillar is 0.21 m

Now, according to given

⟹ curved surface area of cylindrical pillar

= 2*π*r*h

⟹ curved surface area of cylindrical pillar

= 2 * 22/7 * 0.21 * 4

⟹ curved surface area of cylindrical pillar

= 2 * 22 * 0.03 * 4

⟹ curved surface area of cylindrical pillar

= 44 * 0.03 * 4

⟹ curved surface area of cylindrical pillar

= 1.32 * 4

⟹ curved surface area of cylindrical pillar

= 5.28 m²

Here we know that cost of painting each pillar is Rs 7 per m².

Now,

⟹ Cost of painting a pillar = {curved surface area of cylindrical pillar} * Rs 7

⟹ Cost of painting a pillar = 5.28 * 7

⟹ Cost of painting a pillar = Rs 36.96

There are 18 pillars hence,

⟹ Cost of painting 18 pillar = 36.96 * 18

⟹ Cost of painting 18 pillar = Rs 665.28

Answer : The total cost of painting the curved surface area of all pillar's is Rs 665.28

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