Answer :
By formula,
[tex]V=\frac{4\pi r^3}{3}[/tex]Cross multiply, we get,
[tex]\begin{gathered} 4\pi r^3=3V \\ r^3=\text{ }\frac{3V}{4\pi}=\frac{3(268)(7)}{4(22)}=63.955 \\ \\ r=\sqrt[3]{63.955} \\ r=3.999\approx4\operatorname{cm} \end{gathered}[/tex]