Question

two light houses flash their lights after every 20 seconds and 30 seconds.if they flash together at 7:00p.m, when will the light be flashed together again?

Answer 1

Given, Lights flash after every 20 seconds and 30 seconds.

Given, time is 7 pm. = 7 :00 : 00.

Next Flash will be after 20 seconds = 7: 00:20

 Next Flash will be after 20 seconds = 7:00:40

Next Flash will be after 20 seconds = 7:01:00.    ----------------------- (1).


Given time is 7 pm. = 7 :00:00

Next Flash will be after 30 seconds = 7:00:30

Next Flash will be after 30 seconds = 7:01:00    ------------------------ (2).


So, From (1) and (2) equations, we can say that Light will be flashed together again at 7:01 pm.


Hope this helps!