#### 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?

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.