Question

cylindrical roller is of length 2 metre and diameter 84 cm find the number of revolutions it has to make to cover an area of 7920 m square

Answer 1

length=2m=200cm
radius of the roller=84cm=42cm
surface area=2 pi r h
                       2x22/7x42x200
                       52800cm^2
                       5.28m^2
number of revolutions=7920/5.28
                                   1500