10 cylindrical pillars of a building have to be painted

10 cylindrical pillars of a building have to be painted. The diameter of each pillar is 70 cm and the height is 4 m. What is the cost of painting at the rate of Rs.5 per square metre?

  1. Rs.400
  2. Rs.440
  3. Rs.480
  4. Rs.500

Answer

Cost of painting is related to square metre or area (only curved surface area is painted)

Curved Surface Area = 2*π*r*h

Radius = 70/2 cm = 35 cm = 35/100 m

Height = 4 m

Cost = Number of cylinders x Area x Cost per area

= 10 * 2 * 22/7 * 35/100 * 4 * 5

= 440

The correct option is B.