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

How many lead shots each 0.3 cm in diameter can be made from a cuboid of dimensions 9 cm × 11 cm × 12 cm?

1. 7200

2. 8400

3. 72000

4. 84000

A metallic sphere of radius 10.5 cm in melted and then recast into small cones, each of radius 3.5 cm and height 3 cm. The number of cones formed is :

1. 21

2. 63

3. 126

4. 130