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Question
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?
Solution
Diameter of each pillar=`0.5m`
Radius of each pillar` (r) a/2= 0.5/2=0.25m `
Height of each pillar=4m
Curved surface area of each pillar=`2pirh`
= `2xx3.14xx0.25xx4m^2`
=` 44/7 m^2`
Curved surface area of 20 pillars= `20xx44/7m^2`
Given, cost of cleaning= Rs.2.50 per square meter
∴Cost of cleaning 20 pillars = `Rs.2.50xx20xx44/7`
=Rs.314.28.
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