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Railways PYQCBT 2 2017

RRB NTPC · Question 21

Four bells ring at 16, 24, 36, 42 minute intervals. If they ring together at 6.00 a.m. after how long would they next ring together?

  1. 842 minutes

  2. 964 minutes

  3. 886 minutes

  4. 1008 minutes

Show answer & explanation

Answer: (D) 1008 minutes

Explanation

They ring together after LCM(16, 24, 36, 42) minutes. 16 = 2⁴, 24 = 2³ × 3, 36 = 2² × 3², 42 = 2 × 3 × 7, so LCM = 2⁴ × 3² × 7 = 1008 minutes.