Question

A solid metal ball of radius 8 cm is melted and cast into smaller balls, each of radius 2 cm. The number of such balls is
(a) 8
(b) 16
(c) 32
(d) 64

Answer 1

(d) 64

Number of balls = $\frac{\mathrm{volume}\mathrm{of}\mathrm{solid}\mathrm{metal}\mathrm{ball}}{\mathrm{volumeof}1\mathrm{small}\mathrm{ball}}$
= $\frac{{\displaystyle \frac{4}{3}}\mathrm{\pi }\times 8^3}{{\displaystyle \frac{4}{3}}\mathrm{\pi }\times 2^3}=\frac{512}{8}=64$