Railways RRB (Assistant Loco Pilot) Solved Paper-2013

  • question_answer
    The ratio of the radius and height of a cone is \[5:12\], respectively. Its volume is \[314\,\,c{{m}^{3}}\]. Find its slant height.

    A)  13 cm             

    B)  14 cm

    C)  17 cm             

    D)  26 cm

    Correct Answer: A

    Solution :

     Let radius and height of a cone are\[5x\]and\[12x\,\,cm\]respectively, then             \[\frac{1}{3}\times \pi \times {{(5x)}^{2}}\times 12x=314\] \[\Rightarrow \]   \[3.14\times 25{{x}^{2}}\times 4x=314\] \[\Rightarrow \]   \[{{x}^{3}}=\frac{314}{314}=1\] \[\therefore \]    \[x=1\] Since, radius and height will be \[5\,\,cm\]and\[12\,\,cm\]. Now, slan height, \[l=\sqrt{{{h}^{2}}+{{r}^{2}}}=\sqrt{{{(12)}^{2}}+{{(5)}^{2}}}=\sqrt{169}=13\,\,cm\]


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