1.

The diameter of a roller is 84 cm and its length is 120 cm. It takes 500 completerevolutions to move once over to level a playground. Find the area of the playgroundin `m^2`.

Answer» We have, diameter of a roller = 84 cm
r = radius of a roller = 42 cm
h = 120 cm
To cover 1 revolution = curved surface area of roller
`= 2pi rh`
`=2xx(22)/(7)xx42xx120 cm^(2)`
`=44xx720 cm^(2)=31680 cm^(2)`
`=(31680)/(100xx100)m^(2)=3.168 m^(2) " " (because 1m =100 cm)`
Area of the playground = takes 500 complete revolutions
`= 500xx3.168 m^(2)=1584 m^(2)`


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