\(\frac{\log \sqrt{27}}{\log 81}\)

= \(\frac{\log \sqrt{3^3}}{\log 3^4}\)

= \(\frac{\log 3^{\frac{3}{2}}}{\log 3^4}\)

= \(\frac{\frac{3}{2} \log 3}{4 \log 3}\)

= \(\frac{\frac{3}{2}}{4}\)

= \(\frac{3}{8}\)