Question

I need help with this:

On the coast, there are three lighthouses.

The first light shines for 3 seconds, then if off for 3 seconds.
The second light shines for 4 seconds, then is off for 4 seconds.
The third light shines for 5 seconds, then is off 5 seconds.

All three lights have just come on together.
1) When is the first time all three lights will be off at the same time?
2) When is the next time all three lights will come on together at the same moment?
Maybe ill at 20 extra points.......if you get it right thou.
.........and if i can figure out how to. :)

Answer 1

1) The time it takes for each light to complete its cycle is 6 seconds, 8 seconds, and 10 seconds respectively. The three lights will all be off at the same time when they are all at the beginning of their cycles at the same time. The smallest number that is divisible by 6, 8, and 10 is 120. Therefore, all three lights will be off at the same time after 120 seconds.

2) The next time all three lights come on together at the same moment will be when they are all at the beginning of their cycles at the same time. The smallest number that is divisible by 3, 4, and 5 is 60. Therefore, all three lights will come on together at the same moment after 60 seconds.

Answer 2

120 seconds

Explanation: