Question

in a building there are 15 cylindrical pillars the radius of each pillar is 21 cm and height is 4 metre find the total cost of painting the curved surface area of all pillars at the rate of rupees 10 per metre square​

Answer 1

Question :

in a building there are 15 cylindrical pillars the radius of each pillar is 21 cm and height is 4 metre find the total cost of painting the curved surface area of all pillars at the rate of rupees 10 per metre square .

Answer :

$\sf\pink{Given:}$

• Number of pillars is 15 .

• Radius of each pillar is 21 cm.

• Height of each pillar is 4 m .

• Rate of painting is 10 per m² .

$\sf\pink{To\:find:}$

• cost of painting it's curved surface area ?

Explanation :

1 m = 100 cm.

Therefore , 21 cm = 0.21 m.

$\bf\red{Curved\: surface\:area\:of\:1\: cylinder = 2\pi r h}$

$\\ \longrightarrow\sf{ 2\times \dfrac{22}{7}\times 0.21\times 4}$

$\\ \longrightarrow\sf{ 2\times 22\times 0.03\times 4}$

$\\ \longrightarrow\sf{ 44\times 0.03\times 4}$

$\\ \longrightarrow\sf{ 1.32\times 4}$

$\\ \longrightarrow\sf{ 5.28}$

Therefore the curved surface area of 1 pillar is 5.28 m² .

$\bf\red{C.S.A\:of\:15\: cylinder = 5.28\times 15}$

$\\ \longrightarrow\sf{ 79.2}$

Therefore the curved surface area of 15 pillars is 79.2 m².

$\bf\red{Cost\:of\:painting\:15\:pillars = Rate × C.S.A\:of\:15\:pillars}$

$\\ \longrightarrow\sf{ 10\times 79.2}$

$\\ \longrightarrow\sf{ 792}$

Therefore the cost is Rs 792 .

Answer 2

Answer:

Given :

• Number of pillars is 15.

• Radius of each pillar is 21 cm.

Height of each pillar is 4 m.

Rate of painting is 10 per m².

To find :

• cost of painting it's curved surface area?

Explanation:

1 m = 100 cm.

Therefore, 21 cm = 0.21 m.

Curved surface area of 1 cylinder =2π rh

$> 22 \times \frac{22}{7} \times 0.21 \times 4$

•2 x 22 x 0.03 × 4

→→→ 44 x 0.03 × 4

→1.32 x 4

5.28

Therefore the curved surface area of 1 pillar

is 5.28 m².

C.S.A of 15 cylinder = 5.28 x 15

79.2

Therefore the curved surface area of 15

pillars is 79.2 m².

Cost of painting 15 pillars = Rate x C.S.

→→ 10 × 79.2

792

Therefore the cost is Rs 792.