A) \[\text{214}.\text{5}\,\text{c}{{\text{m}}^{\text{2}}}\]
B) \[\text{21}.\text{45}\,\text{c}{{\text{m}}^{\text{2}}}\]
C) \[~\text{215}.\text{4}\,\text{c}{{\text{m}}^{\text{2}}}\]
D) \[\text{21}.\text{43}\,\text{c}{{\text{m}}^{\text{2}}}\]
Correct Answer: A
Solution :
Height of cone\[~=\text{15}.\text{5}-\text{3}.\text{5}=\text{12 cm}\] \[l=\sqrt{{{h}^{2}}+{{r}^{2}}}\] \[=\sqrt{{{(3.5)}^{2}}+{{(12)}^{2}}}=12.5\,cm\] C.S.A. \[=\pi rl~=\text{137}.\text{5 sq cm}\] C.S.A. of hemisphere\[=2\pi {{r}^{2}}=\text{77 c}{{\text{m}}^{\text{2}}}\] \[\therefore \]Total area of the top = 214.5 sq cm.
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