Question 30 Three bells ring at intervals of 4, 7 and 14 minutes. All three rang at 6 AM. When will they ring together again? (a) 6:07 AM (b) 6:14 AM (c) 6:28 AM (d) 6:25 AM
Let the bells ring at 1, 2, 3 minutes
At 6 minutes, all of them ring together.
Now, this 6 is actually the LCM of 1, 2, 3
So, Time when they ring together = LCM of 1, 2, 3
Here,
Time when they next ring together = LCM of 4, 7 and 14
Finding LCM
Thus,
LCM = 2 × 2 × 7 = 28
Thus, the three bells ring together after 28 minutes
Hence, Time when the three bells ring together is 6:28 am
So, the correct answer is (c)

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 13 years. He provides courses for Maths, Science, Social Science, Physics, Chemistry, Computer Science at Teachoo.

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