Question:
Twenty cylindrical pillars of the Parliament House are to be cleaned. If the diameter of each pillar is 0.50m and height is 4m.What will be the cost of cleaning them at the rate of Rs 2.50 per square meter?
Solution:
Diameter of each pillar = 0.5,
Radius of each pillar(r) = d/2
= 0.5/2 = 0.25 m
Height of each pillar = 4 m
Lateral surface area of one pillar
$=2 \pi r h=2 * 3.14 * 0.25 * 4=44 / 7 \mathrm{~m}^{2}$
Lateral surface area of 20 pillars $=20 * 44 / 7 \mathrm{~m}^{2}$
Cost of cleaning one pillar = Rs 2.50 per square meter
Cost of cleaning 20 pillars $=$ Rs $2.50 * 20 * 44 / 7 \mathrm{~m}^{2}=$ Rs. $314.28$