If the ratio of the diameters of the two spheres is 3 : 5, then the ratio of their surface areas is

1. 3 : 5

2. 5 : 3

3. 27 : 125

4. 9 : 25

If two solid hemispheres of same base radius r are joined together along with their bases, then the curved surface of this new solid is

1. 4πr²

2. 6πr²

3. 3πr²

4. 8πr²

If a solid of one shape is converted to another, then the surface area of the new solid

1. remains same

2. increases

3. decreases

4. can't say