The radii of two solid spheres are 10 cm and 20 cm. The ratio between their volumes is :

1. 3 : 8

2. 1 : 4

3. 1 : 8

4. 8 : 3

The given figure shows a solid cylinder and a solid cone on it according to the given measurement, the total surface area of the solid in terms of π and r is :

1. 4πr²

2. 5πr²

3. 6πr²

4. 7πr²

A solid metal cuboid with dimensions 11 cm, 18 cm and 8 cm is melted and identical solid spheres, each of radius 1 cm, are formed. The number of spheres formed is :

1. 378

2. 1134

3. 1512

4. none of these

By applying force on an uniform metallic wire, the wire is extended four times along its length with same width all around. Then :

(i) The volume of metal in both the cases is same.

(ii) The surface area of solid wires in both the cases is same.

Which of the above statements is/are true?

1. only (i)

2. only (ii)

3. both (i) and (ii)

4. neither (i) nor (ii)