Question

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

Answer 1

Answer:

Given, the length of a roller is 40 cm and its diameter is 21 cm.

Now, radius of the roller r = 21/2 cm

Now, lateral surface area = 2*π*r*h

= 2*(22/7)*(21/2)*40        {height = length = 40 cm}

= (22/7)*21*40

= 22*3*40

= 2640 cm^2

=> (21/2)*40        {height = length = 40 cm}

=>Now, area of the room = lateral surface area *number of revolutions

                                    = 2640*300

                                    = 792000 cm2

                                    = 792000(100*100)   {since cm2 = 1/(100*100) m2 }

                                    = 7920/100

 = 79.29 m^2

hope this will help......☺️

Answer 2

Area of room=400×CsA of roller
=400×13.2m
=5280m²