Six bells commence tolling together and toll at intervals 2,4,6,8,10 and 12 seconds respectively. In 30 minutes how many times they toll together.
a) 4
b) 10
c) 15
d) 16
Solution: L.C.M. of 2,4,6,8,10,12 = 120
So they toll together after every 120 seconds i.e. 2 minutes. So in 30 minutes they toll together 30/2 + 1 = 16 times