Question

find the volume of metal used to construct a hollow metallic sphere of internal and external diameters as 10cm and 13cm respectively.

Answer 1

let the external diameter = D = 13 cm
i) external radius = R = D/2 = 13/2  cm
internal diameter = d= 10cm
ii) internal radius = r= d/2 = 10/2  cm

volume of the sphere = 4/3 π [ R³ - r³]

= 4/3 * 22/7 * [(13/2)³ - (10/2)³]
= 4/3 * 22/7 *1/8[ (13)³-10³]
=4/3 *22/7 *1/8 *[2197 - 1000]
= 4/3 *22/7*1/8 * 1197
after cancellation
volume = 627cubic cm