Twenth cylindrical pillars of the Parliament House are to be cleaned. If the diameter of each pillar is 0.50 cm and height is 4m. What will be the cost of cleaning them at the rate of Rs. 2.50 per square metre?

Explanation

The diameter of cylinder `=0.50m` (Given)
Therefore, radius `=0.50/2m`
Radius(r) `=0.25m`
Height `=4m` (Given)
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`
Calculating cost of cleaning:
It is given that cost of cleaning per `m^2` is Rs. 2.50, therefore cost of cleaning 20 pillars is given by:
CSA of 20 pillars x cost of cleaning per `m^2` `=20×44/7×2.5 Rs`.`= Rs. 314.28`Therefore the cost of cleaning 20 pillars of diameter `0.5m` and height `4m` at Rs. 2.50/ `m^2` is Rs. 314.28.