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Railways PYQCBT 2 2017

RRB NTPC · Question 30

A glass containing water has two holes. The 1^st hole alone empties the glass in 9 minutes and 2^nd hole alone empties the glass in 3 minutes. If water leaks out a constant rate, how many minutes will it take if both the holes together empty the glass?

  1. \(\frac{1}{4}\)

  2. \(2 \frac{2}{4}\)

  3. \(3 \frac{1}{4}\)

  4. \(2 \frac{1}{4}\)

Show answer & explanation

Answer: (D) \(2 \frac{1}{4}\)

Explanation

Together the holes empty 1/9 + 1/3 = 4/9 of the glass per minute, so it takes 9/4 = 2 1/4 minutes.