Question:
An irrational number between $\frac{1}{7}$ and $\frac{2}{7}$ is
(a) $\frac{1}{2}\left(\frac{1}{7}+\frac{2}{7}\right)$
(b) $\left(\frac{1}{7} \times \frac{2}{7}\right)$
(c) $\sqrt{\frac{1}{7} \times \frac{2}{7}}$
(d) none of these
Solution:
(c) $\sqrt{\frac{1}{7} \times \frac{2}{7}}$
An irrational number between $a$ and $b$ is given as $\sqrt{a b}$.