Question

Five belss strike at intervals of 6,8,9 and 12 seconds. they they struck simultaneously with a clock at 12 noon which strikes after everyn hour.at what time will they strike together with the clock

Answer 1

LCM of 6,8, 9 and 12 is 72.
It means bells will strike together at every 72 seconds. 
In an hour, there are 60*60 = 3600 seconds
3600 is divisible by 72.
Hence, bells will strike with clock at every one hour.
   Next time it will strike at 1 pm.