Question

There are 12 cylindrical pillars, each of
diameter 56 cm and height 440 cm in a
hall. Find the cost of painting the pillars at
the rate of 50 per sq. m.​

Answer 1

Given:-

• There are 12 cylindrical pillars
• Diameter of each pillar = 56 cm
• Height of each pillar = 440 cm

To Find:-

• The cost of painting the pillars at the rate of 50 per sq.meter

Solution:-

Since pillar is attached to ceiling on the top and to the ground at the bottom, we need to find the area of curved surface.

Hence,

We'll use the formula of curved surface area of the the cylinder.

In question we are given with the diameter of the cylinder.

We know,

• Radius = (Diameter)/2

Hence,

Diameter of each pillar = 56/2 = 28 cm

Let us now convert the units of radius and height into metres.

• Radius = 28 cm = 28/100 = 0.28 m
• Height = 440 cm = 440/100 = 4.4 m

Now,

We know,

• Curved Surface Area of cylinder = 2πrh

Hence,

CSA of single pillar = 2 × 22/7 × 0.28 × 4.4

= CSA = 2 × 22 × 0.04 × 4.4

= CSA = 44 × 0.176

= CSA = 7.744

∴ CSA of one pillar = 7.744 m²

Now,

Since CSA of one pillar is 7.744 m²

Hence,

CSA of 12 pillars = 7.744 × 12

= CSA of 12 pillars = 92.928 m².

∴ CSA of 12 pillars is 92.928 m²

Now,

Cost of painting 1 m² = Rs.50

Therefore,

Cost of painting 92.928 m² = 50 × 92.928

Cost of painting 92.928 m² = 4646.4

∴ Cost of painting 12 pillars is Rs.4646.4.

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Answer 2

This is prefectly explaned answer.

Hope it helps all.

Thanks