If a solid sphere

Volume of a sphere = (4/3)πr³

Volume of a solid cone = (1/3)πr²h

Given, solid sphere of radius r is melted and cast into the shape of a solid cone of height r

Let the base radius be A.

⇒ (4/3)πr³ = (1/3)π × A² × r

⇒ A = 2r