10th Class Mathematics Surface Areas and Volumes Question Bank Surface Area and Volume

  • question_answer
    Three solid glass balls of radii 'r' cm, 6 cm and 8 cm are melted into a solid sphere of radius 9 cm. Find the value of 'r'.

    A)  \[\frac{1}{4}cm\]                            

    B)  \[\frac{1}{3}cm\]

    C)  \[\frac{1}{2}cm\]            

    D)         1 cm

    Correct Answer: D

    Solution :

     Given that the radii of three solid glass balls is 'r' cm, 6 cm and 8 cm, sum of the volumes of the three glass balls \[=\frac{4}{3}\pi {{r}^{3}}+\frac{4}{3}\pi {{(6)}^{3}}+\frac{4}{3}\pi {{(8)}^{3}}\] \[=\frac{4}{3}\pi ({{r}^{3}}+{{6}^{3}}+{{8}^{3}})c{{m}^{3}}\] The volume of the solid sphere of radius 9cm \[\Rightarrow \]\[=\frac{4}{3}\pi {{(9)}^{3}}=243\times 4\pi \] \[\therefore \]\[243\times 4\pi =\frac{4}{3}\pi ({{r}^{3}}+728)\]\[\Rightarrow \]\[r=1\]


You need to login to perform this action.
You will be redirected in 3 sec spinner