A pipe can empty $\left(\frac{5}{6}\right)^{th}$ part of a cistern in 20 minutes. The part of cistern which will be empty in 9 minutes is :

$\frac{3}{8}$

The correct answer is Option (2) → $\frac{3}{8}$

The rate at which the pipe empties the cistern,

$\frac{5}{6}×\frac{1}{20}=\frac{5}{120}=\frac{1}{24}$ of cistern per minute

∴ Part emptied = $\frac{1}{24}×9=\frac{3}{8}$