Class 9 | Chapter 13 | Surface areas and Volumes | Exercise 13.2 | Question 5

Question 5: A cylindrical pillar is 50 cm in diameter and 3.5 m in height. Find the cost of painting the curved surface of the pillar at the rate of ` 12.50 per m2.

Prerequisite

A closed cylinder has 3 surfaces:

  • Curved or lateral surface 
  • Top 
  • Base

The formula to calculate the curved surface area and total surface area are quite simple to learn and derive.

Lateral or curved surface area of cylinder = 2πrh

r = radius, h = height (or length)

Total surface area of cylinder = 2πr ( r + h ) 

r = radius, h = height (or length)

It is recommended to understand the core concept of area, surface area and volume before we attempt any question based on these concepts.

 
Derivation of formula – Surface area of cylinder
 

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