4 Bells toll together at 9:00 A.M. They toll after 7, 8, 11, and 12 seconds respectively. How many times will they toll together again in the next 3 times?

Answer: 5 times

From given, we have,

9:00 AM + LCM ( 7, 8, 11 & 12 )

⇒ 9:00 AM + 1848/60 Min

= 9:00 AM + 30.80 min

• In 3 hours there are = $3600\times 3=10800$ secs.
• Number of times the bell would toll $=\; 10800\; secs/1848$
• Number of times the bell would toll $=\; 5\; times$

After every 1848 secs, they will toll together.

So, The sequence will be 9:00 AM , 9:31 AM , 10 : 02 AM , 10:33 AM, 11:04 AM , 11: 35 AM…

Thus, in the 3 hours, the bells will toll together 5 times.

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