Base circumference of cylinder (c) = 8 cm

So, the radius

\[=\text{ }c/2\pi \text{ }=\text{ }\left( 8\text{ x }7 \right)/\text{ }\left( 2\text{ x }22 \right)\text{ }=\text{ }14/11\text{ }cm\]

Length of the cylinder (h) = 21 cm

(i) If distance covered in one revolution is 8 cm, then distance covered in 9 revolutions = 9 x 8 = 72 cm or distance covered in 1 second = 72 cm.

Thus, distance covered in 4½ seconds

\[=\text{ }72\text{ x }\left( 9/2 \right)\text{ }=\text{ }324\text{ }cm\]

(ii) Curved surface area

\[\begin{array}{*{35}{l}}

=\text{ }2\pi rh  \\

=\text{ }2\text{ x }22/7\text{ x }14/11\text{ x }21  \\

=\text{ }168\text{ }c{{m}^{2}}  \\

\end{array}\]

So, the area covered in one revolution = 168 cm²

Then,

The area covered in 9 revolutions

\[=\text{ }168\text{ x }9\text{ }=\text{ }1512\text{ }c{{m}^{2}}\]

Which is also the area covered in 1 second = 1512 cm²

Therefore, the area covered in 4½ seconds

\[=\text{ }1512\text{ x }9/2\text{ }=\text{ }6804\text{ }c{{m}^{2}}\]