9th Class Mathematics Surface Areas and Volumes Question Bank Surface Areas and Volumes

  • question_answer
    The cost of painting the T.S.A. of cone at \[5ps/c{{m}^{2}}\]is Rs. 35.20 Determine the volume of the cone if its slant height is 25 cm.

    A) \[1223\,c{{m}^{2}}\]          

    B)   \[~1232\,c{{m}^{2}}\]       

    C)   \[~1323\,c{{m}^{2}}\]       

    D)   \[1332\,c{{m}^{2}}\]                      

    Correct Answer: B

    Solution :

    \[T.S.A=\frac{3520}{5}=704\,c{{m}^{2}}\] \[\Rightarrow \]\[\pi r(l+r)=704\Rightarrow r=7\] \[\Rightarrow \]\[h=\sqrt{{{l}^{2}}-{{r}^{2}}}=24\] \[V=\frac{1}{3}\pi {{r}^{2}}h\] \[=\frac{1}{3}\times \frac{22}{7}\times 7\times 7\times 24=1232\,c{{m}^{3}}\]


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