An electronic device makes a beep after every 60 seconds. Another device makes a beep after every 62 seconds. They beeped together at 10 A.M. At what time will they beep together at the earliest?

A
11:00 A.M
B
10:15 A.M
C
9:00 P.M
D
10:31 A.M

Solution:

It is given after every 60 seconds,the electronic device makes a beep.
We know that, the least common multiple (L.C.M) of given numbers is product of highest power of prime factors.
We know that, 1 sec =

160 min

Here, the beep duration of the first device is 60 seconds and the beep duration of the second device is 62 seconds. Understand that, the interval of beeping together is the L.C.M of 60 and 62. Now, the prime factors of 60 and 62 is;