Two spheres of different materials one with double the radius and one-fourth wall thickness of the other are filled with ice. If the time taken for complete melting of ice in the larger sphere is `25` minutes and for smaller one is `16` minutes, the ratio of thermal conductivities of the materials of larger sphere to that of smaller sphere is:

Two spheres of different materials one with double the radius and one-fourth wall thickness of the other, are filled with ice. If the time taken for complete melting ice in the large radius one is 25 minutes and that for smaller one is 16 minutes, the ratio of thermal conductivities of the materials of larger sphere to the smaller sphere is

Two spheres of different material one with double the radius and one fourth wall thickness of the other are filled with ice. If the time taken for complete melting of ice in the larger radius one is 25 minutes and that for smaller sphere is 16 minutes, the ratio of thermal conductivities of material of larger sphere to smaller sphere is

The hollow spheres of different materials one with double the radius and one- fourth wall thickness of the other are filled with ice. If the time taken for complete melting of ice in the large radius one is 25 min and that for smaller one is 16 min , the ratio of thermal conductivities of materials of larger sphere to smaller sphere is

The Thin walled spheres of different matrials one with double the radius and one fourth wall thickness of the other are filled with ice if the time taken for complete metting of ice in the sphere of larger radius is 25 min and that for smaller one is 6min the ratio of the thermal condutivities of the matrials of larger sphere to the smaller sphere is .

Two hollow suphers of same material one with double the radius of the other and double the thickness of the other filled with ice, the ratio of time in which ice gets melted in the two spheres is .

Two vessels of different materials are similar in size in every respect. The same quantity of ice filled in them gets melted in 20 minutes and 40 minutes respectively. The ratio of thermal conductivities of the materials is

Two vessels of different materials are similar in size in every respect. The same quantity of ice filled in them gets melted in 20 minutes and 35 minutes respectively. The ratio of the thermal conductivities of their materials is

Two vessels of different materials are similar in size in every respect. The same quantity of ice filled in them gets melted in 20 minutes and 40 minutes respectively. The ratio of thermal conductivities of the metals is