If a cylindrical rod of iron whose length is 12 times its radius is melted and cast into spherical balls of the same radius, then the number of balls will be :

1. 3

2. 6

3. 9

4. 27

If a solid sphere of radius r is melted and recast into the shape of a solid cone of height r then the radius of the base of the cone is :

1. r

2. 2r

3. 3r

4. 4r

The diameter of a copper sphere is 6 cm. The sphere is melted and drawn into a long wire of uniform circular cross section. If the length of the wire is 36 cm, then its radius is :

1. 0.5 cm

2. 1 cm

3. 1.2 cm

4. 1.5 cm

A spherical ball of radius 3 cm is melted and recast into three spherical balls. The radii of two of these balls are 1.5 cm and 2 cm. The radius of the third ball is :

1. 0.5 cm

2. 1 cm

3. 1.5 cm

4. 2.5 cm