Four different electronic divices make a beep after every 30 min., 1 hr, 1½ hr. and 1hr 45min. respectively All the diveices beeped together at 12 noon. They will again beep together at

• Time-gap after, the devices will beep together = (LCM of 30, 60, 90, 105) minutes.
  
  = 1260 minutes.
  
  = 21 hours.
  
  the devices will again beep after 21 hrs.
  at 9 a.m. the devices will again beep.
• 12 years agoHelpfull: Yes(4) No(0)
• lcm of 30,60,90,105 is =1260 means 21 hours
  so 9AM
• 12 years agoHelpfull: Yes(1) No(0)