Given,
Inclination tallness (l) = 4 cm
Perimeter of upper roundabout finish of the frustum = 18 cm
\[\therefore 2\pi r_1\text{ }=\text{ }18\]
Or on the other hand, $r_1$ = 9/π
Likewise, periphery of lower end of the frustum = 6 cm
\[\therefore 2\pi r_2\text{ }=\text{ }6\]
Or on the other hand\[,\text{ }r_2\text{ }=\text{ }6/\pi \]
Presently, CSA of frustum \[=\text{ }\pi \left( r_1+r_2 \right)\text{ }\times \text{ }l\]
\[=\text{ }\pi \left( 9/\pi +6/\pi \right)\text{ }\times \text{ }4\]
$=\text{ }12\times 4\text{ }=\text{ }48\text{ }cm^2$