Q11 of 79 Page 244

A spherical solid material of radius 18 cm is melted and recast into three small solid spherical spheres of different sizes. If the radii of two spheres are 2cm and 12 cm, find the radius of the third sphere.

Volume of sphere = r3


⇒ (18)3 = (2)3 + (12)3 + r3


⇒ (18)3 = [(2)3 + (12)3 + r3 ]


⇒ (18)3 = [(2)3 + (12)3 + r3 ]


⇒ 5832 = 8 + 1728 + r3


⇒ 5832 = 1736 + r3


⇒ 5832-1736 = r3


⇒ 4096 = r3


⇒ r =


⇒ r = 16 cm


Radius of the third sphere is 16 cm.


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