If four bells toll at intervals of 8,9,12 and 15 minutes respectively. If they toll at 3 pm when will they toll together

Ur basically looking for the common multiple of the numbers 8,9,12, and 15.

LCM of these numbers is 360.

so 360 minutes = (360/60) = 6 hrs

and 6 hrs from 3 p. m. would be : 9 p. m. < = = ur answer