A pipe can empty \(\left(\displaystyle\frac{5}{6}\right)^{th}\) part of a cistern in 20 minutes. The part of cistern which will be empty in 9 minutes is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → \(\displaystyle\frac{3}{8}\)
The pipe empties the cistern at a constant rate, so the part emptied is proportional to the time.
\( \displaystyle \text{part emptied in 1 minute} = \frac{5}{6} \times \frac{1}{20} = \frac{1}{24} \)
\( \displaystyle \text{part emptied in 9 minutes} = \frac{9}{24} = \frac{3}{8} \)