Question

the external radii and the internal radii of the hollow are 3cm and 5cm respectievely and it's height is 21cm .find its volume​

Answer 1

Volume of the sphere = 4/3 π (R3 - r3)

= (4/3) (22/7) (53 - 33)

= (4/3) (22/7) (98)

= 410.67 cm3

Height of the cylinder formed = 8/3 cm

Let the radius of the cylinder be 'r' cm

Volume of the cylinder = πr2h

Volume of the cylinder = 22/7 x r2 x 8/3

                       410.67 = 22/7 x r2 x 8/3  

r2 = 49

r = 7 cm (approximately)

∴ Diameter of the cylinder = 2 x 7 =14 cm