A cylindrical vessel of diameter 4 cm is partly filled with water, 300 lead balls are dropped in it. The raise in water level is 0.8 cm. Find the diameter of each ball.

0.4 cm

Volume of 300 spherical balls = Volume of rise in water level

$⇒300×\frac{4}{3}×\frac{22}{7}×(\frac{d}{2})^3=\frac{22}{7}×2×2×\frac{4}{5}$

$⇒d=\frac{2}{3}=0.4cm$