Answer:
Slant height of frustum \['l'=\text{ }4\text{ }cm\] Perimeter of upper top \[=18\text{ }cm\] \[\Rightarrow \] \[2\pi R=18\,\,cm\Rightarrow R=\frac{9}{\pi }cm\] Perimeter of lower bottom \[=6\text{ }cm\] \[\Rightarrow \] \[2\pi r=6\Rightarrow r=\frac{3}{\pi }cm\] Curved S.A. of frustum \[=\pi l\left[ R+r \right]\] \[=\pi \times 4\times \left[ \frac{9}{\pi }+\frac{3}{\pi } \right]\] \[=\pi \times 4\times \frac{12}{\pi }=48\,\,c{{m}^{2}}\]
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