Diameter of bigger ball = 8 cm

radius of bigger ball = 4 cm

\[Volume\text{ }=\text{ }4/3\text{ }\pi {{r}^{3}}~=\text{ }4/3\text{ }\pi \text{ }{{4}^{3}}~=\text{ }265\pi /3\text{ }c{{m}^{3}}\]

Radius of small ball = 1 cm

\[volume\text{ }=\text{ }4/3\text{ }\pi {{r}^{3}}~=\text{ }4/3\text{ }\pi \text{ }{{1}^{3}}~=\text{ }4\pi /3\text{ }c{{m}^{3}}\]

The number of balls

\[\begin{array}{*{35}{l}}

=\text{ }\left( 265\pi /3 \right)/\text{ }\left( 4\pi /3 \right)  \\

=\text{ }256\pi /3\text{ x }3/4\pi   \\

=\text{ }64  \\

\end{array}\]