Question

In a building there are 22 cylindrical pillars . The radius of each pillar is 28 cm and height is 4 m . Find the total cost of painting the curved surface are of all pillars at the rate of 5 rs. per sq. m​

Answer 1

Answer:

C.S.A. of cylindrical =2πrh

⇒ C.S.A. of are pillar =2×

7

22

×28×4=704cm

2

⇒ C.S.A. of 24 pillars =24×704=16896cm

2

=16896×10

−4

m

2

=1.69m

2

⇒ Total cost Rs. 8×1.69=Rs.13.52

Answer 2

Given :

• There 22 cylinderical pillars.
• Radius of each pillar is 28 cm.
• Height of each pillar is 4 m.

To find :

• Total cost of painting the curved surface area of the all pillars.

Solution :

• Shape of pillar is cylinderical.

$\bf\underline{Conversation :}$

• Radius = 28 cm

• 1 m = 100 cm

• 28 cm = 28/100
• Radius = 0.28 m

As we know,

$\boxed{\pmb{\tt Curved \: surface \: area \: of \: cylinder = 2 \pi r h}}$

$\pmb\leadsto 2 \times \dfrac{22}{7}$

$\pmb\leadsto \dfrac{44}{7} \times 1.12$

$\pmb \leadsto \dfrac{49.28}{7}$

$\pmb \leadsto 7.04$

Curved surface area of one pillar is 7.04 m².

Curved surface area of 22 pillars :

$\pmb\leadsto 22 \times 7.04$

$\pmb\leadsto 154.88$

Curved surface area of 22 pillars is 154.88 m²

So,

1 m² = Rs 5

154.88 m² = 154.88 × 5

$\pmb\leadsto 774.4$

$\bold{\therefore Cost \: of\: painting \: curved \: surface \: area \: is \: RS \: 774.4}$