A dome of a building is in the form of a hemisphere. From inside, it was white-washed at the cost of र 498.96. If the cost of white-washing is र2.00 per square metre, find the
(i) Â Â Â inside surface area of the dome,
(ii) Â Â Â volume of the air inside the dome.
Twenty seven solid iron spheres, each of radius r and surface area S are melted to form a sphere with surface area S'. Find the
(i)   radius r´ of the new sphere,
(ii)    ratio of S and S’.Â
A cube of side 4 cm contains a sphere touching its sides. Find the volume of the gap in between.