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Railways PYQCBT 2 2017

RRB NTPC · Question 102

A water tank has two holes. The 1^st hole alone empties the tank in 8 minutes and 2^nd hole alone empties the tank in 12 minutes. If water leaks out at a constant rate, how many minutes will it take, if both the holes together empty the tank?

  1. \(\dfrac{4}{5}\)

  2. \(4 \dfrac{4}{5}\)

  3. \(4\dfrac{3}{5}\)

  4. \(4\dfrac{2}{5}\)

Show answer & explanation

Answer: (B) \(4 \dfrac{4}{5}\)

Explanation

Together the holes empty 1/8 + 1/12 = 3/24 + 2/24 = 5/24 of the tank per minute, so it takes 24/5 = 4 4/5 minutes.