Question

There is a cylindrical platform of 2m radius 50cm height in the school playground. What will be the cost of white washing the curved surface of this platform at the rate of 12.5 per 100sq.cm ($\pi $ = 3.14)

Answer 1

Hint: In this question remember to find the circumference of the end circle of cylindrical platform and remember to use multiplication operation in circumference of circle and height of cylindrical platform, use this information to approach towards the solution to the question.

Complete step-by-step answer:

According to the given information there is a cylindrical platform with radius 2m and radius 50 cm height
So to find the cost of white washing of curved surface of the platform, let’s find the circumference of circle at the ends of the cylindrical platform
Since we know that the circumference of circle is given by C = $2\pi r$ here r is the radius of the circle and C is the circumference of the circle
Substituting the given values in the circumference formula of circle we get
C = $2 \times 3.14 \times 200$
$ \Rightarrow $C = 1256 cm
So the circumference of circle is 1256 cm
To find the curved surface area of cylindrical platform we have to apply the multiplication operation between the circumference of circle and height of cylindrical platform i.e. circumference of circle $ \times $ height of cylindrical platform
Substituting the given values in the above equation we get
Curved surface area of cylindrical platform = 1256 $ \times $ 50
$ \Rightarrow $Curved surface area of cylindrical platform = 62800 cm² = 628 $ \times $100 cm²
Since it is given that the cost of white washing is Rs. 12.5 per 100 sq.cm
Therefore the cost of white washing curved surface of cylindrical platform = 12.5 $ \times $ 628
$ \Rightarrow $ Rs. 7850
So the cost of white washing the curved surface area of the cylindrical platform is Rs. 7850.

Note: In the above question to find curved surface area of cylindrical platform we multiplied the height of cylindrical platform from the circumference of ends circle of cylindrical platform because we all know that the curved surface of any shape can be defined as the curved surface around the shape is called curved surface area so to find the curved surface area we found the circumference of circle and circumference of circle acted as the curved surface area of cylindrical platform for height 1 cm and since we have to find the curved surface area of cylindrical platform for 50 cm height we multiplied the circumference by 50 times which is height of cylindrical platform and we got the curved surface area of the required cylindrical platform.