Question

three bells toll at intervals of 9,12,15 min, if they started calling together after what time toll together

Answer 1

L.C.M. of 9 ,12 n 15 is 180
so they will ring together. again after 180 min or 3 hrs.

Answer 2

bell one at 9 min
bell two at 12 min
bell three at 15 min

so now finding LCM
we will get answer

LCM of 9,12,15
=2×2×3×3×5
=180

so at time 180 minutes bell will toll together