Question

Four bells begin to toll together and then each one at intervals of 6 s, 7 s, 8 s and 9 s respectively. The
number of times they will toll together in the next 2 hr is:
(a) 14 times
(b) 15 times
(c) 13 times
(4) 11 times

Answer 1

First We have to find LCM of 6, 7 , 8 and 9sec

6= 2×3

7=1×7

8= 2×2×2

9= 3× 3

L.C.M= 2×2×2×3×3×7= 504 sec

LCM of 6 seconds 7 seconds 8 seconds 9 seconds is = 504 seconds

In 1 hour = 3600 seconds In 2 Hours = 3600×2= 7200sec

No. Of times they will toll together in 2 hrs = 7200/ 504 = 14

No. of times they will toll together in the next 2 hr is = 14