1.

Four different electronic devices make a beep after every 30 minutes,1 hour, 1 1/2 hour and 1 hour 45 minutes respectively. All the devices beeped together at 12 noon. They will again beep together at .....(A) 12 midnight (B) 3 a.m.(C) 6 a.m. (D) 9 a.m.

Answer»

The correct option is: (D) 9 a.m.

Explanation:

Convert all the hours into minutes to find L.C.M.
1 hour = 60 minutes
3/2 hour = 80 minutes
1 hour 45 minutes = 105 minutes
Hence we take LCM of (30, 60, 90, 105) = 1260 min = 21 hours. 
So if they ring together at 12 noon today, they will ring together at 9 am tomorrow.



Discussion

No Comment Found