Question

Five bells begin to toll together and toll respectively at intervals of 6,5,7,10 and 12 seconds How many times will they toll together in one hour excluding the one at the start?

• A. 7
• B. 8
• C. 9
• D. 10
• E. 11

Answer 1

The correct option is B 8

All bells will together after exactly 420 seconds (which is the L.C.M of 6,5,7,10 and 12 seconds) or in 7 minutes. So within one hour i.e. in 60 minutes the bells will toll together 8 times excluding the one at the start.