The total surface area of a cone whose radius is and slant height is

If the length of diagonal of a cube is then the length of each edge of the cube is 3 cm.

The radii of two cylinders are in the ratio of 2 : 3 and their heights are in the ratio of
5 : 3. Then, the ratio of their volumes is

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

The radius of a hemispherical balloon increases from 6 cm to 12 cm as air is being pumped into it. The ratio of the surface areas of the balloon in the two cases is