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

The volumes of two spheres are in the ratio 64 : 27. The ratio of their surface areas is

1. 3 : 4

2. 4 : 3

3. 9 : 16

4. 16 : 9