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11th Class Mental Ability Mensuration Question Bank Question - Mensuration

  • question_answer
    Three spherical metal balls of radii 5, 8 and R cm are melted into a solid sphere of radius 12 cm. The value of R is:

    A) 8

    B) 10

    C) 14

    D) 18

    E) None of these

    Correct Answer: B

    Solution :

    Explanation Option (b) is correct. \[\frac{4}{2}\pi {{5}^{3}}+\frac{4}{3}\pi {{.8}^{3}}+\frac{4}{3}\pi {{R}^{3}}=\frac{4}{3}\pi {{(12)}^{3}}\] \[\therefore 125+512+{{R}^{3}}=1728\]                         \[{{R}^{3}}=1091\] \[\therefore \]                  R = 10 (approx.)


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