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 metre?

Explanation

Diameter of cylinder `=0.50m`
radius `=0.50/2m`
Radius(r) `=0.25m`
Height `=4m`
We know,
Curved surface area (CSA) of cylinder `=2πrh`
`=2×22/7×25/100×4`
`=2×22/7`
`=44/7m^2`
CSA of 20 pillars `=20×44/7m^2`
cost of cleaning`=`CSA of 20 pillars x cost of cleaning per `m^2` `=20×44/7×2.5 Rs`.`= Rs. 314.28`