If the external and internal radii of a hollow sphere be 6 cm and 3 cm respectively, then the volume (i.e, the material) of the sphere will be

Options

A. 629 cu-units
B. 792 cu-units
C. 829 cu-units
D. 929 cu-units

Explanation

The required volume of the sphere `=((4)/(3)pixx6^(3)-(4)/(3)pixx3^(3))` cu. units
`(4)/(3)xx(22)/(7)(216-27)` cu.units
=`(4)/(3)xx(22)/(7)xx189` cubic.units= 792 cubi.units
`therefore` (b) is correct