A cone is 8.4 cm high and the radius of its base is 2.1 cm. It is melted and recast into a sphere. The radius of the sphere is

Height of cone, h = 8.4cm

Radius of base, r = 2.1cm

Thus volume of a cone =

Now when it is melted to form a sphere, say of radius r1 cm, the volumes of both are going to be equal.

Volume of sphere

Or

Or

Or

Thus the radius of the sphere is 2.1cm which is option b.