Question

the length of a roller is 40cm and its diameter is 21 cm it takes 300 complete revolutions to move once over to level the floor of a room find the area of the room in m^2

Answer 1

length of the roller = 40 cm
diameter of the roller = 21 cm
radius of the roller = 21/2
c.s.a of the roller = 2×pi×r×h
= 2×(22/7)×(21/2)×40
= (44/7)×21×20
= (44/7)×420
= 44×60
= 2640 cm^2

no of complete revolutions = 300
we know,
area of the floor of the room = area covered by the roller
= 2640×300
= 792000 cm^2
= 792 m^2
therefore the area of the room = 792 m^2