Three bells ring at intervals of 12,15,24 minutes.If they all ring at11:30 am together,at what time will they next ring together?

Number of minutes after which the bell will ring together = L.C.M. of 12, 15, 24

= 2 × 2 × 2 × 3 × 5                       

= 120 minutes

∴ Time at which they will ring together = 11 : 30 A.M. + 120 minutes

= 11 : 30 A.M. + 2 × 60 minutes

= 11 : 30 A.M. + 2 hours

= 1 : 30 P.M.