Multiple choice

An inlet pipe fills a cistern in 3 1 2 hours. However, due to leakage at the bottom, it takes half an hour longer. When the cistern is full, how long would the leak take to empty the cistern?

  1. 28 hours

  2. 27 hours

  3. 29 hours

  4. 32 hours

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The inlet rate is 1/3.5 = 2/7 of the cistern per hour, while the net rate is 1/4. The leak rate is 2/7 - 1/4 = 1/28, so the leak alone empties the cistern in 28 hours.

AI explanation

Using the leak emptying formula, the time taken by the leak to empty the full cistern is given by (filling time multiplied by emptying time) divided by the difference between emptying and filling time. The filling time is 3.5 hours and the total emptying time is 4 hours. Substituting these values gives (3.5 multiplied by 4) divided by 0.5, which equals 28 hours.

Keep practicing — related questions