A hollow sphere of internal and external radii 2 cm and 4 cm respectively is melted into a cone of base radius 4 cm. Find the height and slant height of the cone.
Volume of hollow sphere before melting = volume of cone
Here, R = 4cm, r = 2cm, r’’ = 4cm, therefore
⇒ h’’ = 14cm = height of the cone
Now, slant height, l = 
= 14.56 cm
23