Find the mean proportion of \(\frac{1}{4}\) and \(\frac{1}{81}\) .

\(\frac{1}{22}\) \(\frac{1}{11}\) \(\frac{1}{18}\) \(\frac{1}{16}\)

\(\frac{1}{18}\)

Mean proportion of a and b = \(\sqrt {a × b }\) ⇒ Mean proportion = \(\sqrt {\frac{1}{4} × \frac{1}{81}}\)                                = \(\frac{1}{2 × 9}\)  = \(\frac{1}{18}\)