The square root of 64 / 81 can be expressed mathematically as:
[tex]\sqrt[]{\frac{64}{81}}[/tex]Note that:
[tex]\sqrt[]{\frac{a}{b}}=\frac{\sqrt[]{a}}{\sqrt[]{b}}[/tex][tex]\text{Therefore, }\sqrt[]{\frac{64}{81}}=\text{ }\frac{\sqrt[]{64}}{\sqrt[]{81}}[/tex]Also note that:
[tex]\begin{gathered} \sqrt[]{64}=\text{ 8 and} \\ \sqrt[]{81}=9 \end{gathered}[/tex]Therefore
[tex]\sqrt[]{\frac{64}{81}}=\frac{8}{9}[/tex]