Question

There are 20 cylindrical pillars in a building, each having a diameter of 50 cm and height 4 m, Find the cost of cleaning them at Rs 14 per $m^2$.

Answer 1

ANSWER:
Radius of each pillar, r = 50/2 = 25 cm = 0.25 m
(1 m = 100 cm)
Height of each pillar, h = 4 m
∴ Surface area of each pillar = 2$\pi$ rh=2x22/7x0.25×4 $c{m}^2$
Surface area of 20 pillars = Surface area of each pillar x 20 = 2 x 22/7 x 0.25 x 4 x20 $c{m}^2$
Rate of cleaning = ₹ 14 $m^{-2}$
∴ Total cost of cleaning the 20 pillars
= Surface area of 20 pillars x Rate of cleaning
= 2 x 22/7 x 0.25 x 4 x 20 x 14
= ₹ 1760