Question

The length of a roller is 40cm and its diameter is 21cm. It takes 300 complete revolutions to move once over to level the floor of a room. Find the area of the room in metersquare?

Answer 1

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Given ,length of a roller(h) = 40 cm

and its diameter = 21 cm
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radius(r) = 21 / 2 = 10 .5 cm

lateral surface area of roller = 2πrh

= 2 × 22 / 7 × 10.5 × 40 = 2640 cm^2

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area of the room = lateral surface area of roller × number of revolutions
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= 2640 × 300 =792000 cm^2

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note :1 m = 100 cm => 1 cm = 1 / 100 m

1cm^2 = 1 / ( 100 × 100 )m^2

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therefore area of the room in m^2

=792000 /100 × 100 = 792 /10

= 79.2 m^2

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Your Answer : area = 79.2 m^2
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