four bells toll at intervals of 4,7,12,and 84sec.the bells toll together at 5.00.when will they again toll together?how many times will they do it in 28 min

Given, 4 bells ring at intervals of 4s, 7s, 12s and 84s respectively.

It is given that they ring simultaneously at 5.00.

So, the next time of there simultaneous ring can be find out by taking the LCM of 4s, 7s, 12s and 84s as:

So, the LCM of 4s, 7s, 12s and 84s = 2 × 2 × 3 × 7 = 84

Hence, the bells will toll together after 84 seconds, i.e., at the time 5 : 01 : 24.

Now, in 84 seconds all the bells will toll together = 1 times

So, in 28 minutes (= 28 × 60 s = 1680 s) all the bells will together =