Question

A solid sphere of radius 6 cm is melted and then recast into small spherical balls each of diameter 0.4cm the number of small balls thus obtained is

Answer 1

Whatever happens to the ball the volume of the ball remains same so the volume of the original ball=4Pi r^3 =   4*22/7*6*6*6=....... Divide both the volumes and there you get the answer.
The answer comes out to be27000...

Answer 2

R = 6cm

r = 0.4/2 = 0.2cm

No. of balls = V1 / V2

= 4/3 pi R^3 / 4/3 pi r^3

4/3 pi will cancel each other.

= R^3 / r^3

= 6^3 / 0.2^3

= 216 / 0.008

= 27000 balls

Thanks