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CBSE Class 9 Answered

The diameter of a roller 1 m long is 56 cm. If it takes 200 revolutions to level a playground, find the cost of levelling the playground at the rate of 50 paisa per m2.

Asked by Topperlearning User | 12 Oct, 2017, 07:56: AM
Expert Answer

Given: Diameter = 56 cm ⇒ radius (r) = 28 cm

Length (h) = 1 m = 100 cm

 

Let S be the curved surface area of the roller.

begin mathsize 12px style straight S space equals space 2 πrh
rightwards double arrow straight S space equals space 2 cross times 22 over 7 cross times 28 cross times 100 space cm squared
rightwards double arrow straight S space equals space 17600 space cm squared end style

Area covered in 200 revolutions = 200×17600 cm2 = 3520000 cm2 = 352 m2

begin mathsize 12px style Cost space of space levelling space 1 space straight m squared equals Rs. space 50 over 100
Cost space of space levelling space 352 space straight m squared equals space Rs. space open parentheses 352 cross times 50 over 100 close parentheses equals Rs. space 176 end style

Answered by | 12 Oct, 2017, 09:56: AM
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