Example (18 six bells ring at intervals of 2, 4, 6, 8, 10 and 12 sec, respectively. they started ringing simultaneously. how many times will they ring together

Example (18 Six bells ring at intervals of 2, 4, 6, 8, 10 and 12 sec, respectively. They started ringing simultaneously. How many times will they ring together in 30 min? Solution : LCM of 2, 4, 6, 8, 10 and 12 = 120 . Bells will ring together after every 120 sec or 2 min. Since bells rings together after every 2 min so in 30 min it will ring as (30 min/2 min)= 15 times but at starting (0 sec it also rings so total 16 times.)