JEE Main 2025January, Unspecified (session-level dataset)MathematicsMediumLimit, Continuity and Differentiability420× since 2002
A spherical chocolate ball has a layer of ice-cream of uniform thickness around it. When the thickness of the ice-cream layer is , the ice-cream melts at the rate of and the thickness of the ice-cream layer decreases at the rate of . The surface area (in ) of the chocolate ball (without the ice-cream layer) is: