A cylinder of circumference 8 cm and length 21 cm rolls without sliding for 412 seconds at the rate of 9 complete rounds per second.
The area covered by the cylinder in 412 seconds
Area covered by the cylinder in 1 round = its curved surface area
Given,
Distance travelled by the cylinder in 1 round = it's circumference
Distance travelled in 4.5=4.5× Distance covered in 1 sec
=4.5×9×8
=324 cm
Hence, this is the answer.