Help!!! Lighthouse L has a light which flashes every 12 seconds....!?

N

Nith678

New member
Lighthouse L has a light which flashes every 12 seconds.
Lighthouse M has a light which flashes every 10 seconds.
The two lights flash together at 2 am.

How long will it be before they next flash together?



...OMG help me.. how do I work this out? ;-;
what method do i need to use? show the steps?
thankyou!!
 
You need to find the least common multiple of 10 and 12. The easiest way to do it is to simply start listing out multiples of 10 and multiples of 12 until you find one in common (it won't take long).
 
L will flash at 0:12, 0:24, 0:36, 0:48, 1:00...
M will flash at 0:10, 0:20, 0:30, 0:40, 0:50, 1:00...
so they will both flash at the same time at 1 minute intervals.
 
The interval of time between each simultaneous "double-flash" will be the least common multiple of 10 and 12 seconds, which is 60 seconds.

So, the lights will flash together every 60 seconds; the next occurrence of this will be at 2:01 a.m.
 
Back
Top