• # question_answer If the area of base of a cone is 154 cm2 and height is 9 cm, then the curved surface area of cone will be A)  200.53 $c{{m}^{2}}$            B)  220.53 $c{{m}^{2}}$      C)  240.8 $c{{m}^{2}}$                         D)  250.8 $c{{m}^{2}}$

Correct Answer: D

Solution :

(d): $\pi rl=\pi r\sqrt{{{r}^{2}}+{{h}^{2}}}$ $\pi {{r}^{2}}=154={{\pi }^{2}}=\frac{154}{\pi }\,\,and\,\,r=\sqrt{\frac{154}{22/7}=7}$ $\therefore \pi rl=\frac{22}{7}\times 7\times \sqrt{49+{{9}^{2}}}$ $=22\times \sqrt{130}=250.8.$

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