Question

In a building there are 4 cylindrical pillars. The radius of each pillar is 21 cm and height is 5 m. Find the curved surface area of four pillars.

Answer 1

r = 21 cm
h = 5 m = 500 cm

CSA of one pillar = 2πrh
∴ CSA of 4 pillars = 4*2πrh
= 8πrh
= 8*22*21*500/7
= 264000 cm²
= 26.4 m²

Answer 2

Given:

radius,

r = 21 cm

height,

h = 5 m i.e, 500 cm

To find:

Curved surface area of four pillars = ?

Solution:

As we know,

CSA of 1 pillar = 2πrh

So,

⇒ $CSA \ of \ 4 \ pillars = 4\times 2\pi r h$

⇒                              $=8 \pi rh$

On substituting the values, we get

⇒                              $=8\times 22\times 21\times \frac{500}{7}$

⇒                              $=264000 \ cm^2$

i.e,

⇒                              $=26.4 \ m^2$

Thus, the curved surface are of 4 pillars is "26.4 m²".