Question

in a building there are 30 cylindrical pillars . the radius of each pillar is 42 m and height is 7 m . find the total cost of painting the curved surface area of all pillars at the rate of rs 10 per m sq
​

Answer 1

Given -

• 30 pillars in a building.

• Each of radius 42m

• Each has height of 4m

• Rate = 10 per m²

To find -

• Cost

Formula used -

• Curved surface area of cylinder.

Solution -

In the question, we are provided with the radius and height of 30 cylindrical pillars, and we need to find the cost of painting all the pillars, for that we will First find the curved surface area of one pillar, then we will multiply with area with 30, that will be the curved surface area of 30 pillars, then we will multiply the area with the rate given, to find the total cost. Let's do it!

According to question -

Radius (r) = 42m

Height (h) = 4m

no: of pillars = 30

Curved surface area - $\sf 2\pi\:r\: h$

Where -

π = 22/7

r = radius

h = height

On substituting the values -

$\sf \: csa = 2 \: \pi\: r \: h$

$\sf \: csa = 2 \times \dfrac{22}{7} \times 42m \times 4m$

$\sf \: csa = 2 \times 22 \times 6m \times 4m$

$\sf \: csa = 1056 {m}^{2}$

Similarly -

We will find the curved surface area of 30 cylindrical pillars, by multiplying 1056cm³ with 30.

$\sf \: csa_{(of\:30\:pillars)} = 1056 \times 30$

$\sf \: csa_{(of\:30\:pillars)}=\:31680 {m}^{2}$

Now -

We will find the, the cost, of painting the curved surface, of the cylindrical pillars, by multiplying the area with the rate given.

$\sf \: cost = 31680 \times 10$

$\sf \: cost = rs.316800$

____________________________________________________

Answer 2

Answer:

Given :-

• 30 pillars in a building.
• Each of radius 42m
• Each has height of 4m
• Rate = 10 per m²

To Find :-

Total cost

Formula :-

$\boxed{ \bf CSA = 2\pi rh}$

Solution :-

$\tt \implies \: CSA = 2 \times \dfrac{22}{ \cancel7} \times \cancel{ 42 }\times 4$

$\tt \implies \: CSA = 2 \times 22 \times 6 \times 4$

$\tt \implies \: CSA = 44 \times 24$

$\tt \implies \: CSA = 1056$

Now,

$\bf{CSA \: of \: 30 \: pillar \: = CSA \: of \: 1 \: pillar \: \times 30}$

$\tt \implies \: CSA \tt \: (30) \tt \: = 1056 \times 30$

$\tt \implies \: CSA(30) = 31680$

Now,

Total cost

$\tt \implies \: Total \: cost = 31680 \times 10$

$\frak \purple{Total \: cost = 316800}$