The largest 4 digit number is 9999.We know that , if LCM of given numbers divide a number N , then N is exactly divisible by all the given numbers .LCM of 12,15,18,27 is 540.On dividing 9999 by 540 we get 279 as remainder.Therefore number =9999 - 279 =9720.
L.C.M. of 2, 4, 6, 8, 10, 12 is 120. So, the bells will toll together after every 120 seconds(2 minutes). In 30 minutes, they will toll together 30 + 1 = 16 times. 2
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