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)

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CBSE Class 10 Sample Paper for 2022 Boards - Maths Basic [MCQ]

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 10 years. He provides courses for Maths and Science at Teachoo.