Four bells ring at intervals of 6, 8, 10 and 14 seconds. They start ringing together at 11 a.m. At what time will they next ring together?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → 11:14 a.m.
Each bell rings at multiples of its own interval, so all four ring together again after the smallest time that is a multiple of every interval, the LCM.
\(6=2\times3\), \(8=2^{3}\), \(10=2\times5\), \(14=2\times7\)
LCM \(=2^{3}\times3\times5\times7=840\) seconds
\(840\div60=14\) minutes
11:00 a.m. \(+\) 14 minutes \(=\) 11:14 a.m.
The bells next ring together at 11:14 a.m.