Question

Three bells toll qt intervals of 9,12,15 minutes respectively. If they start tolling together after what time will they next toll together?

Answer 1

ans. is LCM of 9,12,15
LCM(9,12,15)=180
After 3 hours they toll together

Answer 2

Answer:

9 = 3 x 3

12 = 3 x 2 x 2

15 = 3 x 5

the next time they toll together should be their LCM.

LCM(9, 12, 15) = 3 x 3 x 2 x 2 x 5

                       = 9 x 20

                       = 180 minutes    = 3 hours