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# The Diameter of Roller 1.5 M Long is 84 Cm. If It Takes 100 Revolutions to Level a Playground, Find the Cost of Levelling this Ground at the Rate of 50 Paise per Square Metre. - CBSE Class 9 - Mathematics

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ConceptSurface Area of a Right Circular Cylinder

#### Question

The diameter of roller 1.5 m long is 84 cm. If it takes 100 revolutions to level a playground, find the cost of levelling this ground at the rate of 50 paise per square metre.

#### Solution

Given that,

Diameter of the roller=84cm=0.84m.

Length of the roller=1.5m

Radius of the roller =D/2=0.84/2=0.42.

Area covered by the roller on one revolution = covered surface area of roller

Curved surface of roller= 2pirh=2xx22/7xx0.42xx1.5

=0.12xx22xx1.5m^2

Area of the playground="100xxArea covered by roller in one revolution"

=(100xx0.12xx22xx1.5)m^2

=396m^2

Now ,

Cost of leveling 1 m^2=50P=50/100⇒Re=1/2rs

Cost of leveling 396m^2=1/2xx396=Rs.198

Hence, cost of leveling 396m^2 is   198

Is there an error in this question or solution?

#### APPEARS IN

RD Sharma Solution for Mathematics for Class 9 by R D Sharma (2018-19 Session) (2018 to Current)
Chapter 19: Surface Areas and Volume of a Circular Cylinder
Ex.19.10 | Q: 10 | Page no. 8
Solution The Diameter of Roller 1.5 M Long is 84 Cm. If It Takes 100 Revolutions to Level a Playground, Find the Cost of Levelling this Ground at the Rate of 50 Paise per Square Metre. Concept: Surface Area of a Right Circular Cylinder.
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