A cylindrical rod of iron, whose height is equal to its radius, is melted and cast into spherical balls whose radius is half the radius of the rod . Find the number of balls.

A 2
B 3
C 4
D 6

Correct Answer: 6

Let, the radious of each ball is r So, the radius = height of the rod is 2 r So, the number of balls = [π(2r)2 .2r] = [(43)πr3] = 6 
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