Twenty cylindrical pillars of the parliament house are to be cleaned. If the diameter of each pillar is 0.50 m and height is 4 m, What will be the cost of cleaning them at the rate of Rs. 2.50 per square metre?
Number of pillars = 20
Diameter of one pillar = 0.50
∴ Radius (r) = 0.502= 0.25 m
and height = 4 m
Curved surface area of one pillar =2πrh=2×227×25100×4m2=447m2
∴ Total area of 20 pillars = 447×20=8807m2
Rate of cleaning them = Rs. 2.50 per m2
∴ Total cost = Rs. 2.50 ×8807
=Rs.250×880100×7=Rs.22007 = Rs. 314.28