Question

Four bells  are arranged in such a manner that they ring once every 5,8,10 and 12 respectively. After how many minutes of their ringing simultaneously will they ring again together.

Answer 1

see if we have to find when will they ring commonly we will have to find their lcm
and lcm of 5 8 10 12 is 120
means the the first will ring after 24 times
2nd - 15 times
3 - 12 times
4 - 10 times

Answer 2

We find the LCM of 5,8, 10 & 12
We get,
The L.C.M as 120

Which means the bells will again ring after 120 minutes or 2 hours ($\frac{120}{60}$ )